Caro-Kann Defense is a chess opening with the ECO code B10. It goes 1. e4 c6 2. Nc3 d5. White opens with 1. e4 (the king's pawn) and Black answers 1... c6. After 4 moves it is White to move. The lesson on the board explains every move of the line and lets you play it yourself; it is free.
In chessGM's opening book this position continues with 3. Nf3.
Black answers 1.e4 with 1...c6 and then ...d5. It is like the French, but the light-squared bishop can come out first.
chessGM has a full course for this line: open the Caro-Kann Defense course lesson.