The Pennsylvania Municipalities Planning Code is the enabling legislation that authorizes municipalities to enact, amend and repeal zoning ordinances, though they're not compelled to do so. However, if there is a zoning ordinance enacted, it must cover the entire municipality.
A zoning ordinance may "permit, prohibit, regulate, restrict and determine, to the extent not superseded or pre-empted by certain state acts:"
- uses of land, watercourses and other bodies of water
- size, height, bulk, location, erection, construction, repair, maintenance, alteration, razing, removal and use of structures
- areas and dimensions of land and bodies of water to be occupied by uses, structures and open space
- density and intensity of use
- protection and preservation of natural resources and agricultural land and activities
In short, zoning ordinances are what allows local governments to proactively control the ways the properties located in their municipalities is used. This makes zoning an important tool in maintaining the local character of the community, the reason most people chose to live there in the first place.