This may seem like an extremely basic question to an American, but from a European perspective it appears somewhat odd. European countries have a large number of TV stations, some of them public - either tax-funded or funded by means of a TV fee which the population pays directly to the TV station -, and some of them private, earning their revenue from advertising. The concept of TV networks is not present, however, and stations typically broadcast the same programming schedule everywhere in their area of distribution.
From what I gathered from online sources so far, the situation appears to me to be as follows: A network is not a TV station but rather a company which provides content to a large number of different TV stations. These stations are either owned directly by the same company that owns the network, or are affiliated to a network by means of a contract under which they pay money to the network in return for the right to broadcast the network’s program. In other words, the networks operate rather like time slots on the individual stations: Some slots are pre-booked for network content, and the station will air whatever is coming from the network at that time, and other slots are reserved for station content. The slots are, however, the same for all stations affilioated with the same network - it’s not like they show the same shows but they can shuffle them around freely over the course of the day; they would all show the network content at the same time (how does that work across time zones?), and use the same other times for independently produced content. Right so far?
So does that mean that the programming of the individual stations can be split into two parts - one of them content provided by the network, and the other content produced by the individual station itself? Does the station have to cover the entire range of the network’s content, or can it tune out of particular shows if it thinks they’re crap and replace them with own content? Does that mean that two people who live in different cities with different local NBC affiliates (for instance) actually get to see two totally different schedules, even though both of tham would say that they’re watching NBC?
And, also importantly: What exactly is the content that the local stations produce independently? I can see the point of local news coverage, for instance, but you can’t fill half a day with that. And a station which covers only one city or county, for instance, would hardly have the means to produce more elaborate productions. Is it all just syndicated stuff or films for which they purchased local broadcasting rights?