Initiating a minority attack that will dislodge the knight from c3 and oppress White's queenside pawns.
Black immediately exploits the departure of the white knight in order to get a grip on the centre.
After 5...Bxc3?! 6.cxb7 Rad8 7.Rac1 , the passed pawn outweighs the slight material deficit.
After 7...Nd5 8.Bd4 Black is worse due to his queenside weaknesses, but now he loses a pawn.