Chess Opening Theory/1. e4/1...e6/2. Nf3/2...d5/3. e5

White advances the e-pawn into Black's side of the board, hoping to restrict Black's development.

The main move in this position is 3...c5, taking control over the d4-square. This is usually a useful move in the French defence. Making it sooner rather than later allows Black to develop their queenside knight without blocking the c-pawn. Because this move is so common, White is likely to be familiar with the resulting positions, so Black can try to deviate by playing a different move instead:

3...Bd7 delays ...c5 and has the idea of preparing the trade of light-squared bishops with ...a6 and ...Bb5. Black can also choose to transpose into the Euwe variation of the advance French after 4. d4 c5 5. c3 Nc6.

3...b6 also tries to trade light-squared bishops, but this time on a6 instead. Black should be careful, because after 4. c3 Ba6?? 5. Bxa6 Nxa6 6. Qa4+ Qd7 +- White wins a piece, so Black should prepare ...Ba6 with 4...Qd7.

1. e4 e6 2. Nf3 d5 3. e5

Wikipedia has related information at French Defence.