One of the relatively modern flank openings, the English Opening - more about - takes its name from being very popular in English chess in the mid-1800s. It has its own unique lines, but it can also be very transpositional.
Black's normal ("Sicilian") reply is 1..P-K4 (see move 1wb, left) whereupon if White's Centre Variation (2.P-Q4) then the Albin 2..P-Q4 and Budapest 2..Kt-KB3 Counter-Gambits are enabled, but other alternative transpositions into (mostly) Queen's Gambit and QP openings are more likely, for example:
1..e6 Anglo-French Def. leading to Orthodox QGD or to Anglo-Indian Def. or to QP-Indian Def. (for QGD.[Orthodox] or else Nimzo-Indian Def.), or otherwise leading to Indian Def. (for Catalan QGD. or else Neo-Catalan).
1..Nf6 Anglo-Indian Def. leading to King's Indian Defence (with White inviting or avoiding Grünfeld).
1..f5 Anglo-Dutch Def. leading to Dutch Defence.
Symmetrical Four Knights Defence leading to Sicilian Defence.