Public transportation options primarily consist of buses, trains, subways, ferries, and light or metro rail. Transit services are generally run by the cities and counties that they serve, but services that travel longer distances, such as between states, are more commonly provided by private companies.
Transit provided by private companies is generally referred to as "public" if it is shared by strangers. Some examples of private bus companies that provide public transit throughout the United States include Greyhound and Megabus. Amtrak is a unique example of a for-profit company that also receives some federal funding and oversight and provides public intercity train and bus service on both a regional and national level.
States, counties or individual cities usually appoint some sort of a Transit Authority department to oversee public transit in their areas of operation. These services usually charge fares to cover operating costs, but do not operate as private for-profit transportation providers. The services offered can vary greatly by region, but at the very least, some sort of bus service is usually offered by each transit authority. Subways and light rail are available in larger cities, and ferries offer service in cities on the coasts of oceans or major lakes and rivers.