Chess Opening Theory/1. e4/1...c6/2. d4/2...d5/3. Nc3/3...dxe4/4. Nxe4/4...Nf6

= Caro-Kann Defence= This move challenges white's strong e4-knight but allows white to double black's pawns with Nxf6+.

Theory table
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1.e4 c6 2.d4 d5 3.Nc3 dxe4 4. Nxe4 Nf6