The diagram shows the position after 2...dxc4 3.Nf3 Nf6 4.e3 e6 5.Bxc4 c5 6.O-O. Positions with an isolated d-Pawn occur after 6...cxd4 7.exd4.
Most experienced players have an opinion about which side they prefer. The Pawn is strong in the middle game, but weakens as the endgame approaches.
The isolated d-Pawn is strong because it supports a White Knight on both c5 and e5. The Knight on e5 is well placed for a King side attack. The d-Pawn is weak because it can't be protected by another Pawn and is easily blockaded by a Knight on d5. A good example of the play for both sides is seen in the variation 7...Be7 8.Qe2 Nc6 9.Rd1 a6 10.Nc3 Nb4 11.Bg5 O-O 12.Ne5 Nbd5.
Black can also play 6...Nc6, hoping that White will try to gain a tempo with 7.Nc3 Be7 8.dxc5. After 8...Qxd1 9.Rxd1 Bxc5 the extra tempo is useless.