This is the 10114th most frequent Russian word.
бегают
"Бегают" means "they run."
Here, 'бегают' is used to describe the plural action of running.
Дети бегают по двору.
The children run around the yard.
In this sentence, 'бегают' denotes the plural activity of running in a competitive context.
На соревнованиях бегают профессиональные спортсмены.
Professional athletes run at the competitions.
This usage of 'бегают' describes habitual action of cats running.