Not every form of property is physical. Property that exists as ideas is what is known as intellectual property. Like normal property, it is protected by the law. Intellectual property is divided by the law into three main categories. This includes patents, trademarks and copyrights. However, many people may be left wondering what the difference is between these legal terms. A patent refers to intellectual property that protects the specific design of an invention. If a person is granted a patent by the government, it prevents anyone else from using that design during a specific period of time. Usually, this is 20 years from the moment the patent holder filed his or her application. Such an application must include specific information such as what the invention is and how it works. More detailed diagrams may also be included. This could be the design of a mechanical device or a medication. Whatever the case, if that patent is granted, it becomes that person's intellectual property. If anyone else wants to use it, they must license it from the patent holder and pay royalties for its use. A trademark is a bit different. It can protect a name, word or symbol that is used with products that are traded or sold. A trademark is used as signal to consumers. For example, the Pepsi symbol is used to differentiate Pepsi from other soft drinks such as Coke and Dr. Pepper. A trademark, however, does not provide as much protection as a patent. A trademark on the name Pepsi, for example, does not prevent other soft drink producers from introducing a soft drink that tastes very similar to Pepsi. Pepsi's trademarks instead only cover things such as the name Pepsi and the Pepsi symbol that appears on cans and bottles. Like patents, a trademark can be filed with the government. However, one kind of intellectual property that does not really need to be filed with the US Office of Patents and Trademarks is a copyright. A copyright is used to protect things that are known as "original works." An original work can cover many things. It may be a novel, a screenplay, a song, a movie, a painting, a statue or even a videogame. As mandated by federal law, a copyright is the specific property of the creator unless stated otherwise by a previously existing contract. It cannot be used or reproduced by others without the copyright holder's permission.