Townhalls are a type of political event. They are typically small forum events held in places like town halls or school gyms and involve the politician giving a short speech typically limited to a single issue or current event followed by a longer period where the audience asks the politician questions. It’s not limited to campaigning, legislators often hold these events outside of elections. Theoretically they give the politician the opportunity to hear issues and concerns that their constituents most care about but mostly they are used to drum up support for legislation that the politician already supports.