The US Constitution gives Congress the power to “promote the progress of science and useful arts, by securing for limited times to authors and inventors the exclusive right to their respective writings and discoveries.” The USPTO was established to administer patent, trademark and copyright law. In other words, the Office decides what can be patented, and to whom and for how long these rights are granted.
The purpose of granting patents is to protect the inventor for a specified length of time (usually 20 years), thus allowing patent holders to profit from their innovations before they can legally be copied by others. Patent law says that a patent may be issued for a “new and useful” manufactured article, a design, a manufacturing process, machine, or even an improvement on one of these.