Chess Opening Theory/1. e4/1...c5/2. Nf3/2...Nc6/3. d4/3...cxd4/4. Nxd4/4...e5/5. Nb5/5...d6

= Pelikán and Sveshnikov Variations = d6 defends the d6 square with the bishop, and can continue their development smoothly. The knight on b5 now seems to be doing nothing more than attacking d6 and possibly c7 if Black plays very badly, but otherwise is too overextended, so in the future Black plays a6 to prepare b5.

N1c3 is most common.

Theory table
'''1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 e5 5. Nb5'''