Chess Opening Theory/1. e4/1...c5/2. Nf3/2...Nc6

=Open Sicilian with 2...Nc6= Here Black has decided to play Nc6 instead of d6 or other moves. If Black plays pawn to d5 later on then they have saved a tempo by not playing d6 first.

Theory table
1.e4 c5 2.Nf3 Nc6