What kind of music can a cellist play?
All kinds! In addition to hundreds of years of tradition as a classical instrument, it has become very common for cellists to play with rock, folk, and jazz bands. When I was in New Orleans, I recorded for a jazz band, and I’ve played with fiddle players in the Irish and Americana styles as well. For some interesting demonstrations of non-classical cello music, check out on the resources page the website of a colleague of mine, Mike Block, or go on youtube and do a search for the group Apocalyptica.