A 10-second violation in basketball is a rule that the player must cross half court in 10 seconds after their team inbounds the ball. If they do not cross half court in 10 seconds, possession is awarded to the other team. This is a rule for NCAA, WNBA and high school basketball.
A 10-second violation is a bad mistake to make, as teams should be able to advance the ball across the court within 10 seconds.
Teams who are losing late in the game sometimes try to use the 10-second violation to their advantage. If a team does not have possession and doesn't want to foul late in the game, the 10-second violation is one way to quickly get the ball back. If they can stop their opponents from advancing beyond mid-court, they will get the ball back with a chance to win the game.
You may also hear the 10-second violation referred to as the '10-second rule', or hear someone say "they couldn't get half court". These are referring to the 10-second rule.
In the NBA, an 8-second violation is used instead of a 10-second violation.
The backcourt violation plays a big part in the 10-second violation. Remember that the backcourt violation says that once a team crosses mid court, they can not go back to their side of the court. This means if a team is going to cross mid court, they have to be sure that they will stay there. This pressure teams to take longer to cross mid court, meaning there are more 10-second violations.
The 10 second (or 8 second) rule exists to keep teams moving on the court. If players were allowed to remain in the back court for as long as they wanted, the game might not progress as quickly as is typical of the sport. Teams would spend more time in the back court and not be pressuring toward the basket. This rule, along with the backcourt violation, keeps offensive and defensive players closer together, creating a more tight-knit and exciting game.