This is the 11262nd most frequent Russian word.
де
The word "де" in Russian is an archaic or dialectal term meaning "where" or "supposedly."
The word 'де' here is used as a question word equivalent to 'where' in English.
Де вы были вчера?
Where were you yesterday?
Here, 'де' is used to introduce a relative clause, specifying 'the place where' something happened.
Он говорил что-то про место, де произошел инцидент.
He was talking about the place where the incident occurred.
In this sentence, 'де' is again functioning as a question word for 'where'.