Once upon a time the seizure of  this diagonal was considered good enough for equality. Nowadays White  tries to squeeze something out of the position.
1. g1f3  1... d7d5  2. g2g3  2... b8d7 A tricky move order which aims to secure the long  diagonal for the light-squared bishop. 3. c2c4  3... d5c4  4. d1a4 Without a  check. 4... a7a6  5. a4c4  5... b7b5  6. c4c2 