A television network is an entertainment distribution system with a feeder programmer providing programming to TV stations across the country. Prior to the rise of cable and satellite television, a TV station was a single independent entity that received the bulk of its programming from the central network. Now with cable providing national distribution, TV stations have become national networks in their on right.
Reach
A TV station is a single programmer that provides news and network affiliated programming to a local market. A TV network is a group of those local TV stations aligned to provide unified programming. This programming is supplied by a main distributor such as the American Broadcasting Company or the National Broadcasting Company.
Original Programming
Television networks own studios that create the vast majority of their programming. Local TV stations create very little original content, outside of news and public affairs programming.
Distribution
TV networks not only create programming, but they distribute that programming to local outlets across the country. With the advent of cable television, several local TV station became "Superstations" and began broadcasting their programming nationwide.
Use of Public Airwaves
Local TV stations generally broadcast their programming over the public airwaves using digital spectrum licensed by the federal government. Television networks, on the other hand, distribute their programming by satellites.