A lede is the first paragraph or sentence of a news story or article, used to get the reader's attention, let them know what you are writing about, and provide the most basic information in an easily intelligible manner.
In the 1960s enterprising newspaper journalists started to use the spelling 'lede' to refer to the lead paragraph in a news story. This was done to distinguish the homographs lead (intro) and lead (movable type), two words in common usage in the printing trade. 'Lede' is an archaic spelling of lead, and is currently only used in this specific sense. There are still journalists and writers who write lede as lead, although they are currently in the minority.
Ledes are an important part of writing, and as such they have been analyzed and criticized, described and bastardized. Here's a quick guide to some types of ledes and misledes:
Hard Ledes:
Direct, factual, and to the point.
Blind lead: My favorite type of lede, a blind lede assumes that the audience you are writing for knows nothing about the subject. You don't start with an exciting and engaging hook, you start with a short, clear statement of what the subject is and why one should care. After you've oriented your audience you can include a more traditional lede in the next line, or as the first sentence in the second paragraph.
Summary Lede: Perhaps the most traditional lede, at least in reporting; it seeks to report the core context right up front, often planned to address the five Ws (who, what, when, where, why, and sometimes how).
Straight Lede: Direct and to the point. Generally a thesis statement or summary of the piece.
Round-up lead: A lede that tries to introduce multiple topics. This sounds bad, but it isn't always. "Robin Hood is not only a classic English folk story, but also an animated Disney feature, a comedic musical, and a new film starring Russell Crowe." If you are actually able to interrelate all topics in the lede into a cohesive essay, more power to you. Just remember that ledes are supposed to be simple introductions. If your lede is a tangled mess, it doesn't speak well for the rest of the piece.
Soft Ledes:
An intro that is less direct, using some sort of hook to engage the reader before getting to the hard work of informing them.
Anecdotal Lede: A lede that tells a story, introduces interesting characters, and attempts to get the reader interested on a interpersonal level rather than laying out the facts of the story. "John has been walking down these streets for hours, looking for a job. He has a wife and 16 children waiting at home, and he is worried that he will not be able to buy them food for dinner tonight if he doesn't find work soon."
Question Lede: Opens with a question (e.g., "Who really discovered the true meaning of Christmas?"), hoping to engage or intrigue the reader.
Zinger Lede: A short, grabby lede that grabs the reader's attention, generally despite conveying little information. A zinger lede is so clever, interesting, or even confusing that the reader reads more, either because they like the voice or tone of the article ("Sometimes it’s the princess who kills the dragon" --
Susan Leonard), or they have been presented with a mystery that they must solve ("His last meal was worth $30,000 and it killed him." -- Edna Buchanan).
Delayed lead: Also known as a feature lede, because they are often used in feature articles. These are hardly ledes at all, as they can take multiple paragraphs to set the stage.
Dos and Don'ts:
Backing into the lede: Closely related to the blind lede, this is when you include the most interesting information at the end of the introductory sentence or paragraph. Saying that someone is backing into the lede is essentially a criticism of their writing; if you thought the delayed lede was a good choice you would indicate this by calling it a blind lede or other more positive phrase.
Backing into the lede is extremely common amongst the grammatically inclined, and some of the oddities of journalistic grammar arise from a dread of backing onto the lede. Here is an example of backing into the lede: "Noted scientist Bob Marley reports finding mutant rats in New York". Here is the approved newsspeak version: "Mutant rats invade New York, reports scientist". The eye catching phrase comes first, the boring parts later. This is closely related to the first verb principle, which asserts that the first verb the reader sees should describe the most important 'what' of the story. 'Rats invade' is exciting, 'scientist reports' is boring. Don't blame the journalists, blame the fickle public.
Buried lead: Even more extreme, burying the lede refers to hiding the lede paragraphs or even pages into the piece. This is less common than backing into the lede, but is more obviously annoying, so is a more common criticism among the general public.
It is common advice to keep ledes short and to the point, kill your darlings, use the active voice, and keep it simple. This will all depend rather a lot on what you are writing, and the context in which it appears -- a blog post is not a newspaper article, and shouldn't be. It is also useful to remember that the lede doesn't need to do too much work; you have a whole article to expand upon your topic. However, if needed, a lede may be followed by a nut graf, which gives a bit more information and context to the story.