An arena is an enclosed area, often circular or oval-shaped, designed to showcase theater, musical performances, or sporting events. It is composed of a large open space surrounded on most or all sides by tiered seating for spectators. The key feature of an arena is that the event space is the lowest point, allowing for maximum visibility. Usually, an arena is designed to accommodate a fairly large number of spectators.
The term arena is sometimes used as a synonym for a very large venue such as Pasadena's Rose Bowl, but such a facility is typically called a stadium. The use of one term over the other has mostly to do with the type of event. Football is typically played in a stadium while basketball and hockey are typically played in an arena, although many of the larger arenas hold more spectators than do the stadiums of smaller colleges or high schools. And there are exceptions. The home of the Duke University basketball team would qualify as an arena, but the facility is called Cameron Indoor Stadium.
The term "arena" is also used loosely to refer to any event or type of event which either literally or metaphorically takes place in such a location — often with the specific intent of comparing an idea to a sporting event, such as "the arena of war" or "the arena of love" or "the political arena". In many fighting games, the stage that opponents are fought in is also called an arena.