mhensley said:
What is the difference between a developer and a designer? In my world (web developer), a developer writes code and a designer is in charge of graphics.
Well, this is a bit of an oversimplification, since the two duties overlap, but:
A designer at WotC is basically a writer. They're responsible for coming up with, and then putting into words, the book's conent. (I am, technically, a "freelance designer.") The lead designer is the guy who outlines the book, and to whom the other designers deliver their text for a first round of editing, development, and red-lining.
A developer is one of the people who then goes back over that text, scouring the mechanics with a fine-toothed comb, and making changes, corrections, and additions as necessary. In many cases, the development team might add or replace entire chunks of content, which would technically make them co-writers. This might be done to fill in holes in the word count, or to replace sections that are just not viable mechanically or thematically. (For instance, if I'm not mistaken, the dread necromancer class was added to
Heroes of Horror by the development team; I don't think either James or C.A. created it, and I know I didn't.) If it helps, although the metaphor isn't 100% accurate, the developer is to the mechanics and game-play elements what an editor is to grammar and spelling. Often the lead designer does a first round of development before the actual development teams delves into the book in more detail.
Now, all that said, many times someone who's usually on the development team will serve as a designer--that is, writer--on a particular book. And sometimes someone who is normally a staff designer--say, such as James Wyatt--will instead join the development team for a particular book. So the lines aren't hard and fast, but that's the basic gist of it.