Copyright is simply that: the right to copy. The holder of a copyright is the person who legally owns that right. Most of the time the copyright holder is the creator of the work (the author, composer, painter or photographer) although that is not aways the case.
More specifically, copyright is the legally secured right of the copyright holder of a creative work to control the reproduction of that work. Other rights of the copyright holder include the right to distribute copies of the work, to adapt the work, and to perform and display the work publicly.