The Chebanenko Slav is a variation in the Slav Defense. It starts with the moves:
1. d4 d5
2. c4 c6
3. Nf3 Nf6
4. Nc3 a6
White has a few options but the main line is for white to continue with 5. e3. It solidifies the central pawn chain and opens things for the light square bishop. Now black plays 5…b5. Part of the reason that black plays a6 is to prepare for b5. Black is all in on trying to undermine the central pawn structure for white with a full attack with all of the queen side pawns.
This also keeps white from exchanging on c4 and ending up with a bishop on c4. This is what normally happens in the Slav exchange. Because of this, white can get confused on the best way to attack the Chebanenko Slav.
To watch an overview of the Chebanenko Slav you can check out the video below.