i never played queen's gambit like this!


i was surprised when he did that...i thought he will play e6 or c6

That's the Symmetrical Variation of the Queen's Gambit Declined, also called the Austrian Defense. I first encountered it when the Bluebush Chess computer program as Black played it against me. A few grandmasters have played it, and MCO 12 said it's not clear if it's sound, so it can't be too bad, despite the widespread perception that it (and the closely associated Tarrasch Defense) are weak. A few generalities:
Almost any 3rd move by White is good, but forcing moves are stronger. 3. cxd5 is the most popular. 3. e3 is passive, less strong, and commonly transposes to the Tarrasch Defense. The resulting game regardless of White's 3rd move is technically drawish because pieces (especially queens) are traded off quickly and pawn structures are usually balanced, but the defense requires a lot of memorization by Black to avoid losing in the opening, since there are so many options at every move, and it's a very open game, which always incurs the risk of quick loss by Black if there is a single misstep. Many principles of ordinary Queen's Gambit variations apply, such as that White must not try to hang onto his gambited pawn via b4, and either side can end up with a classic isolani.