Government at the national level is meant to deal with issues that affect the whole country. However, not all issues bear attention at the national level; some are more state-level issues while others are ones that local area governments can handle.
Local governments come in many different sizes often predicated by a particular geographic area. The exact form of government that local units can have is often something that is decided at the state level. Some states will have two different tiers, county and municipal. Others will go with strictly county level while others will eschew those for municipal level ones.
The importance of local government goes back to the earliest days of the country. When the colonies were initially settled, there was not a whole lot of influence exerted by the British monarchy over them. The day to day operations and rule of the different towns and cities fell to the people in those specific areas.
Although the Constitution gave the power to form local governments to the states via the tenth amendment, the Census Bureau (a federal agency) has seen fit to categorize the different local governments across the country:
* County: these are considered first-tier local governments. Most states are divided into them or a form of them, i.e. boroughs, parishes.
* Sub-county: these are usually municipalities or townships depending on how they were formed
* Municipality: unlike counties that are divided according to geographic area, these are centered on a particular population base; cities, towns, boroughs (except in Alaska), and villages are included in this category.
* Townships: unlike municipalities, these are formed as part of a division of a particular county
Local forms of government do have some of the same functions as the state and federal government like the ability to levy taxes (to a degree). Unlike the state government, who has the powers that the Constitution does not give to the federal government, the local level entities only have what powers the state specifies.