A council is a group of people that gathers for the purpose of giving advice or making decisions. If you’re president of the student council, for example, you might organize people to get the hallways at your school painted purple.
Council comes from the Latin word concilium for "group of people, meeting," which is what it basically means today. There are student councils, honor councils, or city councils, to name a few. People working together to take care of business — that’s a council. Of course, that council might give advice, or counsel (with an s) people on what to do. Not the same word — an honor council might counsel a principal about how to address cheating in school, for example.