Who was Joel?
Joel was a prophet of Israel and son of Pethuel.
The name ( יואל , yō'ēl), meaning "Yahweh is God," seems to have been common, as we find a dozen other persons bearing it at various periods of the Biblical history. Beyond the fact that he was the son of Pethuel, there is no intimation in the book as to his native place, date, or personal history; nor is he mentioned in any other part of the Old Testament; so that any information on these points must be matter of inference, and the consideration of them must follow some examination of the book itself.
IBSE (in the public domain) with minor edits.