This is a position from the Philidor opening variation, and Be7 is a verycommon mistake. After that, Black gets big problems because of the f7-weakness.4....Be75.dxe5Nxe55...dxe56.Qd5Andthere's no way to defend on f7.Nh67.Bxh66.Nxe5dxe57.Qh5And Whitewins material. f7 and e5 are hanging.