A period in basketball is a block of time that a basketball game is made up of. Rules regarding periods differ between leagues and associations. There are four periods in an NBA game that last 12 minutes each, in FIBA basket and women's NCAA basketball, there are four, 10 minute long periods. In all those cases, periods are also called quarters, since it represents one quarter of a game. In NCAA men's basketball, there are only two periods lasting 20 minutes each. The time in all periods in a basketball game is called the regulation time. If after regulation there is a tie, teams will play extra time.
After every period there is a break. If a game is played in the 4 period format, there is a short break between periods 1-2, and 3-4; and a big, fifteen minute break during periods 2-3, which is called halftime break. NCAA men's basketball games only have the halftime break.