Basketball games are made up of quarters and halves. In the NBA, basketball games have four quarters. In men's college basketball, there are two halves in a game. Together, these quarters and halves are called regulation. The game clock counts down to the end of each quarter and/or half.
A longer break from play called halftime happens halfway through every basketball game. In the NBA, halftime happens after the 2nd quarter. In men's college basketball, halftime happens after the 1st half.
Some halftime shows have contests, like having a fan try and hit a half-court shot for money. Other halftime shows have giveaways like free t-shirts for fans. They keep the crowd engaged during this gap in the game.
In the NBA, the team that starts with the ball after the 1st quarter is determined by which team won the tip-off. The team that wins the initial jump ball will receive the ball in the 4th quarter, while the other team gets the ball for the start of the 2nd and 3rd quarters. The ball is inbounded at the baseline opposite the attacking basket.
In college, the possession arrow determines which team gets the ball to start the second half. The possession arrow points toward the team that loses the tip-off, then switches direction after each jump ball scenario. Instead of having a jump ball on every held ball, college referees award possession based on the possession arrow.