Explain what a city council is, what kinds of decisions it makes, and that voters elect its members to represent them.
Most cities and towns are run day to day by a mayor and a city council (in some rural areas, a county board of supervisors does a similar job). Council members are not born into the job or hired like an employee -- local voters elect them, meaning the council is supposed to represent what the people living there actually want.
A city council makes decisions about local matters: whether to build a new park, how to spend money on roads or the library, what local rules (called ordinances) to put in place, and how to keep the community safe and running smoothly. It usually meets regularly, in public meetings that any resident can attend.
Mastery looks like: They can explain that a city council is elected by local voters and name at least two kinds of decisions it makes.
Common stumbles: Confusing a city council with the state or national government, or assuming council members are simply hired rather than elected.