This is the 5532nd most frequent Russian word.
полагают
"Полагают" means "it is believed" or "they suppose."
In this sentence, 'полагают' is used impersonally to express an assumption or a general belief.
Полагают, что древние пирамиды были построены для религиозных целей.
It is assumed that ancient pyramids were built for religious purposes.
Here, 'полагает' reflects the subject's personal assumption or belief.
Он полагает, что сможет закончить проект вовремя.
He assumes that he will be able to finish the project on time.
This usage of 'полагают' indicates a belief or assumption shared by many people.