[FEN ""] 1. d4 c5 2. d5
A lot of people play it against me as black, and I am also interested in it for both sides.
What are some of the main lines? Also, what are some of the key positions and ideas?
As white I have had a pretty easy time following up with the moves c4 - Nc3 - e4 - f4. Black will usually play e6 and exd5 - respond with cxd5. White ends up with a ton of space in the center. Look up the Taimanov variation in particular.
Basically I got this from MCO15 - the author mentions that many players use a different move order to reach the Benoni just to avoid this setup (they wait for white to play Nf3 blocking the f pawn).