Ever downloaded a great sound track that you wanted to use in the game, but then you found out it just plays from start to finish, and starts playing again from the beginning?
However, if you listen to some of the BGM's that come with RPG Maker, such as the battle themes, you'll notice that they have the intro part, but then it will just keep playing forever.
This is accomplished through a concept called "looping". Basically, let's say you had a 60 second song, and you wanted the part between 15 and 45 seconds to keep playing. You would specify that at the 15 second mark, you would like to start looping, and at the 45 second mark, you would end looping.
Now, your audio file starts playing from the beginning of the song. Once it reaches the 15 second mark, it will notice that it's entered a loop. It will continue to play until the 45 second mark, where it notices that it's at the end of the loop. Now it goes back to the beginning of the loop, and starts playing the song at 15 seconds again.
Normally, this information is set in the music files themselves. However, with this plugin, you can use a simple spreadsheet to maintain audio loops for all of your music files!
This also means you can create different kinds of loops for the same music file if you wanted to, without distributing multiple copies of the same file.