Copyrights give the copyright owner exclusive rights over their original works. While not all works are copyrightable, a few examples of copyrightable materials include movies, literary works, live performances, sound recordings, radio broadcasts, and even software. On the other hand, ideas, concepts, and facts cannot be copyrighted, and in order for a work to be eligible for a copyright, it must be in a fixed tangible form, such as a drawing on paper.
As a copyright owner, you have certain rights that are exclusive to you, such as the right to display your work, distribute your work, make derivative works (a digital version of a published book, for example), and reproduce your work. You also have the right to authorize an agent to exercise your exclusive rights or transfer your copyright, in whole or in part.
Generally speaking, a copyright can be transferred to another party through an assignment or a license. An assignment means that you sell or give the copyright to another person or entity, which would result in your loss of copyright control. If you grant someone a copyright license, on the other hand, you are still the owner of the copyright, but the person who is granted the license (the licensee) can legally exercise some or all of the copyright owner's rights. A copyright license is a practical option for copyright owners who wants to maintain control over how the licensee uses the rights.
If you've composed a written work or song that you wish to promote commercially, you will want to license your work to allow others to distribute or perform it for a fee. A license may be exclusive or nonexclusive and can be restricted by factors such as purpose, territory, duration, and media.
An exclusive license allows only the party who signed an agreement with you (the licensee) to exercise the right being licensed. A nonexclusive license allows multiple licensees to exercise the same rights being transferred in the license.