Locating text inside a cell
=FIND(search_for, text_to_search, [starting_at]) =SEARCH(search_for, text_to_search, [starting_at])
Both return the position where the text first appears. The difference: FIND is case-sensitive, SEARCH is not. If the text isn't there, both return #VALUE!.
The real use is feeding that position into LEFT, RIGHT or MID to split text that doesn't have a fixed length:
=LEFT(A2, FIND("@", A2) - 1) → username of an email
The - 1 stops just before the @.