“A corner kick is the method of restarting play in a game of association football when the ball goes out of play over the goal line, without a goal being scored and having last been touched by a member of the defending team. The kick is taken from the corner of the field of play nearest to the place where the ball crossed the goal line. Corners are considered to be a reasonable goal scoring opportunity for the attacking side, though not as much as a penalty kick or a direct free kick near the edge of the penalty area. It is legal to directly score from the corner kick. When a goal is scored in this fashion it can be called an Olympico goal, and less commonly the English equivalent Olympic goal. …”
Wikipedia
YouTube: Corners really aren’t that effective. Here’s how they could be better.

Alessandro Del Piero taking a corner kick for Sydney FC.