these were a series of drum machine's released by roland in the 80's (if i'm correct) released around 10'000 units per model, everything from the tb-303, to the tr-909, they all have there signature sounds, and they became widely used for hip hop/early drum & bass production, but most commonly acid house in the late 80's/early 90's, to the current date, an example of this being (kanye west's love lockdown), the 808 kit has some good sounds for dubstep in my opinion.
i'm pretty sure that's near enough right?