This move order belongs to the Réti Opening. White offers a temporary pawn sacrifice in order to get rid of the central black pawn. Black can accept the pawn sacrifice with 2...dxc4, but White has no problem recovering the material by means of 3. e2-e3 or 3. Qd1-a4+. A more solid option for Black is to protect his pawn with 2...e7-e6 or 2...c7-c6. He also has the strong thrust 3...d5-d4, which seizes space in the centre. In the Réti Opening White mostly fianchettoes his light-squared bishop to g2. The development of his remaining pieces will depend on what his opponent plays.