A work-for-hire is the creation of a work (text, art, an invention, etc.) for an employer. All rights for the works are assigned to the employer or the entity that commissioned the work. When signing up with a publisher of books or music, make sure that the contract does not assign all of your rights to the pubisher. Some contracts assume all of the rights to the work, so it is up to the creator to decide if they want to release their rights in exchange for money, fame or exposure. Some people consider this release to be "selling out".