Chess Opening Theory/1. e4/1...c5/2. Nf3/2...e6/3. d4/3...cxd4/4. Nxd4/4...Nc6/5. Nc3/5...Nf6

=Sicilian - Four Knights Variation= Black deploys their knight to f6, where it puts pressure on the pawn on e4. One of Black's main idea in this position is to play Bb4, where it would pin the white knight and threaten to take it on e4.

Theory table
1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 Nc6 5.Nc3 Nf6