The Fixture endpoint provides information about Games in particular Leagues. There are always two teams involved in a Fixture. For many customers, Fixtures is the main endpoint for their app/website. Be aware your access is limited to Fixtures of Leagues, available in the Plan you are subscribed to.
Responses of the Fixture endpoint are highly customizable because there are many Includes available to extend the response. Requests often start with the Includes localTeam and VisitorTeam. Events, Stats, Lineups, Comments, Trends etc. are often added as well.