May be different in different states. In Indiana it is a government unit smaller than a county but larger than a town. Mostly, each county in Indiana has 6 to 9 townships. Some of them do things like local fire departments, parks and such. In Indiana, most school districts are at the township level unless they are a city school system. Our state is looking at getting rid of most township functions and rolling them up to cities or counties to save money. They were more valuable in the past when things were more rural. (Township school districts are good though - I think smaller districts are more responsive).