What is Scrivener?
Scrivener is a writing and composition software developed and sold by Literature and Latte. It provides a huge number of robust and easy-to-use features, which can be daunting to new users. It is available on Mac, Windows, but not available on Linux. It is designed to make writing much easier and faster by allowing the user to organize their documents in a heiarchy tree, tag, color-code, and open their notes side-by-side, as well as add custom meta-data. There's similar software out there such as Manuskript, but Scrivener is more intuitive to use and has more features (which is expectable, considering Scrivener is $50 and Manuskript is free). The Windows version is slightly behind the Mac version; the software was originally available solely for Mac, and they started development for Windows much later; the Windows version is still in "version 2" while the Mac version is in "version 3", but the company claims the Windows version will catch up eventually. The projected date keeps getting pushed back though, so don't hold your breath.
(Some) features of Scrivener
Scrivener is pretty feature-heavy, so I have decided to give each main feature its own subsection (as opposed to simply listing them in a couple of lengthy paragraphs). They're not listed in any particular order of best to worst, simply in the order that they come to mind. There are many small features other than these; these are just the major ones.
Note and document organization
There is a sidebar on the left-hand side that hosts all the text files, images, folders, documents, etc. of the project in a hierarchy . You can simply click and drag elements into sections or subsections for them to be listed under that section. You can group files into folders and then set an icon for that folder, there is a large list of icons to choose from. You can also put the documents in your manuscript into folders; it will still export any file in the manuscript section, regardless of the folder. The folder can be for an act-structure, sections, etc. You can right-click on any document to assign a "status" to it, which color-codes the document. When writing longform fiction, I personally color-code my manuscript documents based on what character it's written from the perspective of. You can also assign a "label" to each document, such as "to-do", "first draft", "second draft", and so forth. The label will appear on each document when in the corkboard screen. You can also create custom meta-data.
The ability to edit or view two documents side-by-side
You can split the editor right down the middle and open up any two documents in the sidebar with a singular click. In Microsoft Word you would need to open each file in the file browser, which doesn't sound like much, but being able to switch with the sidebar with just a click saves so much time and effort. You can have note or reference text opened up beside your main document. You can split the window vertically or horizontally. You can also open up an image or imported webpage. I personally appreciate this feature the most.
Various writing tools
You can highlight any word or phrase in your currently-opened text and search with a built-in Dictionary, Google, Wikipedia, Dictionary.com, BrainyQuotes, and translate the text to another language. There is also a very powerful name generator, probably the best one I've ever seen. You can select from dozens upon dozens of nationalities and ethnic groups for both the first and last name, choose the gender, and character you want the names to start and end with, select the number of names to generate, and let it do its work. I've gotten great character names from this, such as Alexey Varenkov, Farah Nazarri, Yvonne Leski, among others. It also has a very good inbuilt name-meaning finder, in which you can enter a name and it will show the meaning in every nationality and culture that the name has a meaning in. For example, Nicolas has definitions in French, Greek, Jewish, and Spanish (all variations of "victorious conquerer" and "victory of the people".) You can also import your own lists of names in bulk simply by listing the names in a plain text file with a comma between them and then importing the file to be used in the generator.
A minimalistic fullscreen "Zen" editor
You can choose to edit your currently selected document in a minimalistic editor, which gets rid of all the various UI elements, sidebars, formatting options, etc. and just displays the text over a blank background. You can customize the width of the text-editing box as well as the display-size of the text. You can choose a color to have the background display as (I have mine set to completely black with white text so that it's easier on the eyes), or you can set the fullscreen editor to have any desired image as the background.
A "corkboard" mode
You can view all the files under a category or folder in a "corkboard" mode, in which it displays them all in index cards, lists their status "to-do, first draft, etc." and their "synopsis" metadata (which you can assign just by double-clicking the index card and typing on the card itself, as opposed to opening some bulky metadata editor from the properties menu). It allows you to see the progression of your text, and in my current project it allows me to see if anything needs to be added or removed between two sections.
Automatic formatting to industry-standard
The manuscript and front-matter folders of your text is automatically set up for export-inclusion, while all the other folders are not. You can select a huge variety of options depending on the type of project you're working on; ebook, novel manuscript, screenplay, etcetera. It automatically exports to industry standard, which means you don't have to do any of the work of formatting your pages, putting your last name and page number in the header, etc. If you're writing a screenplay, it behaves as a screenplay editor and not simply a rich-text editor; it automatically switches to the correct margins and indentations for the various elements of the screenplay and whatnot.
"Where can I learn more?"
You can purchase it from their website here.
A link to information about the upcoming update to the Windows edition of Scrivener can be found here. According to the page, "If you buy Scrivener 1 for Windows now, you’ll get a free update to version 3 when it’s available." However, they also say "Existing users of Scrivener 1 will be able to purchase Scrivener 3 for the discounted price of $25 when the time comes", which implies the upgrade will not be free. Do with that what you will.