Alekhine's defence - two pawns' (Lasker's) attack
1. e4 Nf6 2. e5 Nd5 3. c4 Nb6 4. c5
White moves the king's pawn to e4. Black develops the knight to f6. White pushes the king's pawn to e5.
Black moves the knight to d5. White pushes the c-pawn to c4. Black transfers the knight to b6.
White plays the c-pawn to c5.