White has many possible plans in this system. This is one of the popular choices right now. The pawn push is useful because the bishop will go back after a7-a6, and Black will not have the chance to play b7-b5.
1. e2e4  1... c7c5  2. g1f3  2... d7d6  3. f1b5  3... b8d7 This and 3...Bd7 are the most popular moves. My old favorite, 3... Nc6, is not enough for equality.