This is the 4442nd most frequent Portuguese word.
caem
"Caem" means "fall" (third-person plural present tense of the verb "cair").
Here, 'caem' is used as the verb 'to fall', indicating the action performed by the subject 'leaves' during autumn.
As folhas caem no outono.
The leaves fall in autumn.
In this case, 'caem' again represents the verb 'to fall', describing the subject 'they' experiencing the action of falling from the stairs.
Eles caem da escada com frequência.
They fall off the stairs frequently.
Here, 'caem' denotes a figurative usage of 'to fall', referring to the decrease in prices during a promotional event.