A typical idea: the knight attacks the bishop and then goes back.
1. c2c4  1... e7e6  2. g2g3  2... d7d5  3. f1g2  3... g8f6  4. g1f3  4... f8e7  5. e1g1  5... e8g8  6. d2d4  6... c7c6  7. b1c3  7... a7a5 A curious move that is quite popular these days. The pawn advance can be useful in case of a plan with ...b6-Ba6. 8. f3e5  8... b8d7  9. c1f4 