Normally Internet radios play music by default, often resulting in a lot of songs you don`t like. But this doesn`t happen with Spotify, where you can look for and select the music you want to listen to.
In Spotify you have an internal searcher to look using different criteria, like genre, artist, theme, etc. That means you can find exactly what you want. Once you have made that selection, you just have to play it, and listen to it all via the Internet.
Spotify is totally free, but on the author`s website you have other versions (Day Pass and Premium) with which, for a daily or monthly price, you can access a much bigger music catalogue.