Here is a true discovered attack (not a discovered check) by a pawn. The most likely tip-off to the idea is the presence of the two queens on the same line—here, a diagonal. (It pays to be sensitive to alignments of all sorts.) If the pawn between them can vacate the diagonal and give check at the same time, Black can play QxQ a move later. So f4-f3+ wins. It's very simple. You might also have noticed this, of course, by just considering every possible check and its consequences—the lines it opens, etc. It takes some time to internalize the idea that a pawn on the same diagonal as a bishop or queen is such a powerful tactical weapon.