From the very beginnings radio has come a long way of development. It has become very sophisticated and diverse. Instead of using only FM and AM broadcasting, there are many ways of broadcasting. Here is the list of most common categories of radio stations divided by the way of broadcasting.
First category is the national radio. Those are all the biggest radio stations which are broadcasted national wide. That means they are available only in one specific country or state. Those can be either independent commercial broadcasts or stations that are controlled by government or other national force. This is one of the most popular types of radio stations which attract huge numbers of listeners. Usually they are broadcasted in FM frequencies.
The next ones are local or regional radio stations. These radio stations are broadcasted in lot smaller areas, so they have a lot less listeners. Usually also the quality of these kind of stations is lot lower, but locals still listens, because mostly there are some local news provided. They can be broadcasted either in FM or AM frequencies.
Then there is satellite radio. They transmit signals through antennas and they are broadcasted through satellites. The principles of it are similar to cable TV. That means it is possible to reach a lot wider areas and also provide lot higher sound quality and selection of radio programs. Unfortunately it is not possible to listen to these types of stations using traditional analog or digital radios. There is a need for specific satellite radio or other device that can perceive these signals.
Internet radio or podcasts are stations that are broadcasted through the internet, not using the radio waves or satellite signals. The variety of internet radio stations is huge. Almost anyone can make an internet radio station and broadcast it whole day long. That is why there are many low quality internet stations, but there can be found something good as well. Some of the most popular internet radio stations also use other broadcasting ways as well.
Collage of non-profit radio stations are very small, independent broadcasters. They are broadcasted in very small areas. Usually they are made to play music of some unknown artists or to start a career as a radio DJ and prove the professional abilities. There are lots of these small radio stations, but they are quite unpopular.
The last type is pirate radio. Actually those are FM channels that are not regulated. They are illegal and usually broadcast some kind of controversial or unwanted content. They are made for many reasons, but mostly they have some political backgrounds, for example to spread some political ideas through the audience.