Undermining White's centre, and clearing the f-file and the a1-h8 diagonal for his own pieces.

Seizing the bishop pair.

Increasing the pressure on f4 and preparing ...e6-e5.

Again preparing ...e6-e5, with an excellent game for Black.

Preparing Qg4 and f4-f5 with an attack.

Now this advance gains strength due to the unsafe position of Black's king.

9...0-0 would be better.

10...Bxg5 11.Nd6+ +-

With an extra pawn and a strong attack, White is winning.