There are currently 8 Sports in Nintendo Switch Sports.
How To Play
To play a sport, first select one of the 3 modes from the main menu. You should then arrive at Spocco Square, the main hub for the game. From here, you can select any one of the 8 sports available to play.
Options
You can choose from a few options when entering a game. These vary from game-to-game, but one that stays consistent is which side arm/leg you would like to use. For example, in Soccer/Football, you can choose either right leg or left leg to shoot with, and in Tennis, Badminton, Chambara, Volleyball, Bowling, Golf, and Basketball you can choose either right or left for your dominant hand.
Pro League
Main article: Pro League
In each sport, there is a skill-based Pro League that you can enter after winning a certain amount of games, in which you can slowly rank up from E to ∞ (A before version 1.2.0), and play against people of similar rank.