What is the origin of the idiom "the green-eyed monster" and when to use it?

The phrase "the green-eyed monster" comes from William Shakespeare's play Othello. In the play, Iago describes jealousy as the green-eyed monster, suggesting that it can consume and distort a person's thoughts and emotions. It is used to describe the emotion of jealousy, especially when it leads to irrational or possessive behavior.