A patent is issued by a federal government to an inventor or applicant that allows the patent owner to prevent others from making, using, selling or importing an invention in the country in which the patent is granted. Typically, the patent protects the invention, or its functionality, so long as the invention in new, useful and nonobvious.
A trademark is used to identify a product. It identifies the source of the good and that helps a customer identify the product so the customer can have an expectation of the quality or other characteristics of the product or service. Trademarks protect. Likewise, the trademark helps build reputation for the entity that sells the goods by allowing the customer to associate the trademark with the goods. Service marks work the same way, but for services instead of goods.
When a work (writing, music, screen play, photograph) is created, a copyright vests in the work. Depending on when the work is created, and by whom, determines how long the copyright lasts. To enforce your copyright, the copyright must be registered with the Copyright Office of the United States Library of Congress.
Agreements are used to transfer intellectual property from one entity to another. Agreements are also used when licensing a set of rights from one entity to another. When rights are being transferred, the deal or agreement must be in writing.