The English Opening happens when White starts the game with the move 1.c4. White refrains from moving their d and e-pawns and instead uses a flank pawn to control the center.

White's first move allows for more versatile play with the center pawns by both sides. The game mainly revolves around who will get to solidify their grip over the center of the board.

Usually, White will play with a Sicilian-like setup with colors reversed or the game will transpose into a queen's-pawn opening. The latter is another reason behind White's move: it avoids or limits Black's responses to some defenses against 1.d4 openings.

Pros
Fights for the center with a wing pawn
Can lead to queenside pressure
Takes many Black players out of their comfort zone

Cons
Slower development
Less direct attacking chances
Allows Black to put a strong pawn on e5