Chess Opening Theory/1. d4/1...Nf6/2. c4/2...c5/3. d5/3...b5/4. cxb5/4...a6/5. bxa6/5...Bxa6

= Benko Gambit =

5. ... Bxa6
The most common move. 5... g6 is more flexible. Here in case white continues b3 to oppose the black bishop on g7, black can't capture with the knight on a6 to pressurise d5.

Theory table
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'''1. d4 Nf6 2. c4 c5 3. d5 b5 4. cxb5 a6 5. bxa6 Bxa6'''