The Reti Gambit is an aggressive approach to attack the French Defense and it starts with the moves:
1. e4 e6
The e6 move signals the French Defense and play usually continues:
3. Bb2 dxe4
White gives up the e4 pawn for rapid development on the queen side of the board and the ability to keep the board wide open. As white playing e4, the French Defense is something many players don’t want to see and this opening gives white multiple variations to continue the aggressive nature of an e4 opening while thwarting many of the ideas a typical French Defense player has.
If black tries to hold onto the pawn they will generally find themselves with a weakened pawn structure heading into the end game while not being able to actually hold onto the material advantage.
If black lets white easily retake the pawn on e4 then white can castle on either side of the board while having a huge lead in development.
Make sure you check out the video below to learn more about all the variations.