This is the 10698th most frequent Polish word.
dowiedzieli
"Dowiedzieli" means "they found out" or "they learned."
The word "dowiedzieli" is used here in the past tense to indicate that someone gained knowledge of the truth.
Dowiedzieli się prawdy.
They learned the truth.
In this sentence, "dowiedzieli" is conjugated for the first person plural form, emphasizing the collective gaining of information.
Dowiedzieliśmy się o tym wczoraj.
We found out about it yesterday.
"Dowiedzieli" is used in the question to inquire whether someone has gained the knowledge about the subject matter.