There are many audio formats. The most important that differenciate each format is the quality and the size.
For instance, mp3 is one of the formats that takes less space and also one with the worse quality loss compared to the original recording, even if most of people don't notice it. Compared to mp3, flac and ogg can take twice more space but have no quality loss.
Here's a very bad idea record label had. A DRM is a digital protection that can be placed in a audio file before it is sold that let the vendor restrict what you can do with your audio file. Softwares that are not compatible with the DRM technology can then just not play the file so that caused a lot of problems.. only to honest people who buy their music. So before buying online, you might want to make sure that your purchase won't contains DRM.
Audio editing softwares
Audio playing softwares
Windows Media player