This is the 837th most frequent Croatian word.
otišli
"Went" or "left" (past tense, plural).
In this sentence, 'otišli' is used as the past participle form of the verb 'otići', indicating that the subject (we) went to a specific location.
Mi smo otišli u kino sinoć.
We went to the cinema last night.
Here, 'otišli' signifies the moment in the past when the action of leaving for the trip occurred, associated with 'your parents' as the subject.
Kada su tvoji roditelji otišli na putovanje?
When did your parents leave for the trip?
In this example, 'otišli' describes an action completed in the past where the subject (they) left a certain city a long time ago.