What does the term "side out" mean in volleyball?

The term "side out" in volleyball specifically refers to the event when a team loses the serve to the opposing team. This occurs after the serving team fails to score a point and the receiving team wins the rally, allowing them to take over the serve. This concept is crucial in volleyball as it emphasizes the competitive nature of the game where teams can switch between serving and receiving based on their performance in rallies. As a result, understanding "side out" is essential for comprehending the flow of the game and the strategies teams utilize to regain and maintain service.

The other options relate to aspects of volleyball but do not accurately define what a "side out" means. For instance, switching players or player substitutions pertain to team management and strategy during play, while serving and scoring points are integral to gameplay but do not encapsulate the direct implication of losing the serve, which is what "side out" signifies.