Since 2006, maybe even 2005 or earlier, web designers and developers have been hearing this term "Web 2.0" uttered by coworkers or seeing it appear in blogs. Sometimes it's used in marketing. Sometimes when meeting with other designers and developers it's said in an almost hushed tone, like the person has just discovered the secret of the Next Big Thing ("Whoah, that's Web 2.0!"). It's even been wielded as a weapon, an instrument to hit you over the head repeatedly. The biggest question about this lauded, much-ballyhooed, even sometimes maligned term is:
"So what the heck is Web 2.0 anyway?"
That is a very good question. When you figure it out, could you please tell me?
That's a typical response. But fear not fellow web-heads! I will attempt to answer it to the best of my ability.
Origin
First, let's quickly go over the term's origin. The first O'Reilly Media Web 2.0 conference in 2004 is where the term initially popped up and arguably it was really just marketing-speak at first, the real meaning of which to be decided later. According to Tim O'Reilly, "Web 2.0" "...is the business revolution in the computer industry caused by the move to the Internet as platform, and an attempt to understand the rules for success on that new platform." In other words, it's about how developers and end-users use the web and its technology, not necessarily actual new technical specifications. In fact, a criticism of Web 2.0 is often that we've had about the same specifications back since the days of Web 1.0. But anyway, about the only useful thing O'Reilly has said that I think has any sticking power when you're talking about nailing down a definition of Web 2.0 is the phrase "Internet as platform." This means that it is using the web as a means to create information - often content creation and/or authoring as in with blogs - not simply to display information. Using the internet (or web, which I think makes more sense) as a platform also is about building applications and services around the features of the web and/or internet that some of have come to love, some of us have come to revile, instead of building the apps and expecting the web to conform to them, which would be fighting the internet. ("Don't fight the internet" has been adopted as a slogan by O'Reilly for Web 2.0, a phrase originating from Google CEO Eric Schmidt.).
Characteristics
Web 2.0 websites can often be compared to desktop applications. Whether one agrees with the viability of the term and its reality or not, the fact is that websites more and more are taking on the look and usability of traditional applications. The advent of Content Management Systems (CMS) and Ajax (Asynchronous Javascript and XML) has made this possible. And consequently, depending on how a website is using this technology, a big feature of Web 2.0, one most individuals seem to agree with, is the allowance of users owning their own content. Like this website, Everything2, for example. Or related to this, user-contributed content, as is the case with Wikipedia. This is also where Weblogs, or blogs for short, come into play. Really, the whole concept of a communal website, either in part as in with Amazon (user reviews and responses to the reviews) or in whole as in with this site, the whole idea of contribution and social networking, is Web 2.0-ish. You can blanket all this with the general idea of interactivity on a website, an idea that's been bandied about since well before anybody ever uttered "Web 2.0."
Search Engine Optimization - or SEO - is often spoken about somewhere in a discussion of Web 2.0. Crosslinking in blogs, or blog-like sites, appears to drive traffic to a site a lot more than to sites that don't have that feature. This isn't really a characteristic, but more a side effect, of having a Web 2.0 site. Besides crosslinking, another major factor to consider is the content. Content is King with Web 2.0. The idea that websites should no longer be marketing, static monoliths, but rather a living, breathing, ever-changing content-based sites (that still look nice, of course) is an important one in Web 2.0. Websites should always be in beta, as it were.
Technology
The aforementioned Ajax is essential to many websites deemed Web 2.0, a technology that allows a website to have many features of desktop applications like wizards, movable and resizable windows and/or modules (which, as any web developer or designer might know, are usually DIV layers), drag and drop, interpage scrolling - basically anything that can reduce or even eliminate the pesky Web 1.0 problem of page loading and reloading. Some web applications, like Sitecore, a CMS that's often used at my company, use so much Ajax that it actually resembles a PC desktop in look and functionality!
Flash, which used to be widely regarded as cool-looking but really a nuisance getting in the way of somebody just trying to get to the information he or she really came to the website for, has evolved well beyond mere eye candy to dazzle a websurfer. It can be used in much the same way Ajax is, to make a website into a rich application with capabilities that are almost only limited by the designers' and developers' imagination. There are still some issues with Flash, especially in terms of SEO, but this constantly-evolving technology is changing right now - probably as you're reading this - to correct this problem. In a year or two this will be an issue of the past.
OK, OK Silverlight, too. Calm down, Microsofters.
Valid XHTML and HTML markup is essential in the vague world of Web 2.0. And while on this subject, Microsoft's new XAML language will be a big part of this Web 2.0 movement, too.
There's something called "folksonomies" which, to be honest with you, is a term I am not fond of. I guess it's taxonomy for... folks. But anyway this has to do with tagging.
Cascading Style Sheets, or CSS, is a must for a website, Web 2.0 or not. They facilitate Separation of Presentation and Content. These handy tools, which has been around well before the term Web 2.0 was born, are finally becoming widely used and standardized (hacks for Mozilla and Internet Explorer in style sheets are becoming less and less necessary). Without going into a sub writeup about CSS, I'll just say that essentially it's about quickly changing and updating the look of a site without ever having to touch the webpage file.
Weblog publishing tools and wiki or forum software are essential for user-generated content.
XML and RSS are also often considered into the sphere of Web 2.0.
There are many other things that my knowledge of is limited at best, like web APIs, and if I were a developer - I'm more of a designer - I'd be able to honestly tell you a lot more about them.
Design
In terms of what a Web 2.0 site looks like, i.e. colors, structure, and presentation, this is more vague and undefined than its supposed technology and features. From what I can see, some common design elements of alleged Web 2.0 websites are bigger text (as in, 12 point or larger - years ago the trend was to use smaller and smaller text), bigger line height, massive use of gradients, clean and simple, pastel colors (some claim contrasting colors which contradicts that), and large header areas (things that are typical of a lot of blog sites). As far as anything else goes, I cannot really come up with much that's really solid in this area.
Criticism
Is "Web 2.0" a buzzword? Certain people I know that will remain nameless use the term waaaaaaaaay too much. Almost every new site he discovers that he thinks is cool, he says "Check it out, man, that's Web 2.0!" or sometimes just, maddeningly, with a smug nod, "Web 2.0!" It certainly seems to me sometimes to be nothing more than a buzzword. The fact is, ask ten different people what it means and you're likely to get at least eight different answers. Too many individuals, like my coworker, it seems, especially marketing folk, are using the term ad naseum, effectively trying to stomp it into the ground and pound out any meaning from "Web 2.0" that we actually have been able to almost agree upon. It may have always been meaningless, but if it wasn't, it's quickly becoming meaningless now. It would be wise if people would lay off the term some until we can all figure out exactly what it means, if anything, but I don't think anybody will listen to me.
Is "Web 2.0" real? Misuse of the term, I think, is making it more unreal and meaningless all the time. The Wikipedia definition of the website (a supposed Web 2.0 website itself) is currently "a trend in web design and development — a perceived second generation of web-based communities and hosted services (such as social-networking sites, wikis, blogs, and folksonomies) which aim to facilitate creativity, collaboration, and sharing between users." If everybody could agree on that, that would be swell. But marketing people are throwing it around to describe any website they want to draw attention to or market as the latest, greatest thing to ever hit the web. And web designers, at least in my humble opinion, are becoming too consumed with designing a website that looks like "Web 2.0" before they understand what all that might entail.
I conclude that, sadly, it is mostly a buzzword and, frankly, I'm sick of it. The internet and the World Wide Web are constantly changing, constantly evolving, and the direction it is headed in is good and exciting and I'm glad to be in the industry. The point is, we really don't know what exactly is in store for this "information superhighway" (another buzzword that thankfully died a looong time ago) and who knows what the face of the web will look like in 20, 10, or, hell, even 5 years from now. My mind boggles at how I will be designing and/or developing a website when I am nearing retirement age. So what? Are we going to start saying "Web 3.0" in a few years? "Web 4.0" a few years beyond that? Or will we get really silly, saying "Web 2.1" or "Web 3.2.1??" How about we just keep up with the technology and design trends that are allegedly Web 2.0 because, hey, it's all good. It's all simply about a Rich User Experience and we don't any catchy term for that.
Let's just stop with the buzzwords and enjoy the ride because it's going to be at times a bumpy, but mostly an exciting one.
Sources: http://en.wikipedia.org/wiki/Web_2.0, a WebBuilder 2.0 conference, and my own experiences in the industry.