This is a more wordy, narrative accompaniment to my pretty bare presentation about d3 that I gave to the jQuery DC Meetup.
- Not a chart library (though you can make charts with it)
- Not a map library (though you can make maps with it)
Which is to say, d3 can be used for building things, but the 'atomic parts' are lower-level than bar graphs or projections or so on. This is a powerful fact. It also means that d3 is a good basis for simple interfaces, like Vega.js, that make its power accessible in other ways.
- Not a compatibility layer (it doesn't work with bad browsers)