When talking about a player platoon system in sports, it’s usually in regards to baseball, a sport which utilizes a platoon system more than any other. Depending on what handedness the opposing pitcher is or how the opposing lineup is setup, a team can start one player over another depending on their respective strengths.
Platoons exist in many other sports and can be known by different terms depending on the league. In the NBA, this tactic is known as load management and is something employed by almost every team to limit the wear and tear on their star players.