Chess Opening Theory/1. e4/1...e5/2. d4/2...d6

This is an inferior way to enter a Philidor. While White's best move is still Nf3, transposing into the Philidor, it gives the additional option of immediately entering an endgame with 3.dxe5 dxe5 4.Qxd8+ Kxd8 5.Bc4 (though engines have no trouble defending it for Black). Black would lose the right to castle, and White would have a lead in development. White can also enter a Chekhover-like position via 3.Nc3 exd4 4.Qxd4 with the intention to respond to Nc6 with a Bb5 pin, or alternatively drawing the queen back to d3 or e3 and simply enjoying a space advantage. As such, it is considered strictly inferior to the Philidor move order, because White's alternatives after 1.e4 e5 2.Nf3 d6 are much less aggressive.