Why is the word BONUS beneath a score?

Obviously I don’t see much basketball these days, and the game has changed since I used to watch it fairly early in the last millenium. In a game that was just on TV, at one point the word BONUS was beneath one team’s score and later it was under each team’s score. What is that all about, please?

from Wikipedia

There is also a Double bonus, which means that, when a team has accumulated enough fouls, for each subsequent foul they commit, the opposing team gets to make 2 free throws instead of one (as is the case in the Bonus).

Before a team is in Bonus, a foul will only result in free throws if the foul was committed on a player that was attempting to make a basket.

Okay, many thanks to you both. I’ve got to start remembering to look into places like Wikipedia first.