In tennis, an Insurance Break is when a player wins two service games against their opponent.
This gives the player a bigger lead in the set. It's called "insurance" because it provides extra protection against losing the set. With an insurance break, a player can lose one of their service games, and still be ahead.
This makes it harder for their opponent to catch up. Getting an insurance break can be a turning point in a match. It puts a lot of pressure on the opponent to win back both breaks.