A tournament is a quiz bowl competition. The term may mean an event taking place over one to three consecutive days (usually Saturday, or including Saturday), but may also refer to an extended event like a league or conference in which gameplay is split over many days over a course of weeks or months.
Tournaments can be broadly classified as local or national, by level (middle school, high school, community college, college, or open), and in other ways.
The QBWiki has some categories pertaining to tournaments, but they are very incomplete:
There is also a guide on how to run a high school tournament that is not actually limited to high school tournaments, but could use some updating.