Definition
The legal right of the creator of an original work, such as a video, song, photo or text, to control copying and use; it exists as soon as the work is fixed.
What it means
Copyright protects original works of authorship, including videos, music, photos, writing, artwork and software. Under U.S. law it exists automatically as soon as the work is fixed in a tangible form, such as recorded or saved, and gives the owner exclusive rights to copy, distribute, perform, display and adapt it. Registration with the U.S. Copyright Office is not required for protection, but for U.S. works it is needed before suing for infringement and brings other legal benefits. Ideas, facts and short phrases are not protected. Creators can license their work to others, for example when a brand pays for usage rights, and income from licensing may be royalty income.
Example
A filmmaker owns the copyright in her short film the moment she saves the final edit, and she registers it before releasing it to keep the right to sue if it is copied.
Illustrative numbers only. Your situation will differ.