What does Judges 9:7 mean?

When Jotham heard about this, he climbed up Mount Gerizim, stood where everyone could hear him, and shouted, 'Listen to me, people of Shechem, so God will listen to you.' Judges 9:7 - Modern Text Bible

(Jotham, Gideon's youngest son and the only survivor of Abimelech's massacre, calls out to the people from a mountain, trying to get their attention and warn them.)