Chess Opening Theory/1. d4/1...d5/2. c4/2...e6/3. Nc3/3...c5

=Tarrasch Defense=

3...c5
Black aggressively attempts to gain space in the center, with the caveat of an isolated pawn on d5 after a few pawn exchanges.

Theory table
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'''1. d4 d5 2. c4 e6 3. Nc3 c5'''