We have music with two types of licenses: Standard Music License and Creative Commons.
Standard Music License means you need to purchase one time license but you will be free from paying any royalties further. You will receive a copyright notice which you can dispute by using license file. Claim will be released within 24 hours.
Creative Commons - means that you free to share, copy and redistribute the material in any medium or format; adapt, remix, transform, and build upon the material for any purpose, even commercially. But you must give appropriate credit (name of author and song) and provide a link to original track.