警报是一种声音或信号，用来告诉大家有危险，要小心或者快点离开。

A 警报 is a sound or signal used to warn people of danger, telling them to be careful or leave quickly.

比如火灾的时候，警报会响，大家听到就会跑出去。

For example, during a fire, the 警报 will sound, and everyone hearing it will run outside.