In the Breyer Variation, black knight hops onto the e4 square thereby allowing for the exchange of the knight. This is rather a more balanced structure for black which helps in the offense and the defense. The bishop if present on c5 would have been at the offense but on the e7 it is being prepared for both cases.
1.e4 e5 2.Nc3 Nf6 3.f4 d5 4.fxe5 Nxe4 5.Nf3 Be7 6.Qe2 Nxc3 7.dxc3 c5 8.Bf4 Nc6 9.0-0-0 Be6 10.h4 Qa5 11.a3 Rb8 12.Bg5 b5 13.Bxe7 Kxe7 14.Qe3 b4 15.cxb4 cxb4 16.a4 Qxa4 17.Qc5+ Kd7 18.Nd4 Rhc8 19.Bb5 Rxb5 20.Nxb5 Nxe5
This move blunders a piece.
In the Oxford variation,Bishop variation,Breyer Variation,Three Knight's Variation, Boden-Kieseritzky Gambit,Alekhine Variationand Reversed Spanish Opening,unlike some of the previous openings these can be played even in longer formats of the game as they are less riskier and positional to be played and hence played more by the high level of chess players.