This is the 469th most frequent Slovak word.
sú
"Are" (third-person plural present tense of "to be").
The word 'sú' is used here as the third-person plural form of the verb 'to be' (byť) to state a fact about the existence or condition of the subject.
Títo ľudia sú priatelia.
These people are friends.
In this sentence, 'sú' is again the third-person plural of 'to be,' used here to inquire about the presence of something (questions) in or at a specific place.
Sú tam nejaké otázky?
Are there any questions?
Here, 'sú' serves to link the subject ('houses') to its composition or characteristic ('made of bricks').