Before you can get on the air, you need to be licensed and know the rules to operate legally. US licenses are good for 10 years before renewal and anyone may hold one except a representative of a foreign government. In the US there are three license classes—Technician, General and Extra.
The Technician class license is the entry-level license of choice for most new ham radio operators. To earn the Technician license requires passing one examination totaling 35 questions on radio theory, regulations and operating practices. The license gives access to all Amateur Radio frequencies above 30 megahertz, allowing these licensees the ability to communicate locally and most often within North America. It also allows for some limited privileges on the HF (also called "short wave") bands used for international communications. Learn More
The General class license grants some operating privileges on all Amateur Radio bands and all operating modes. This license opens the door to world-wide communications. Earning the General class license requires passing a 35 question examination. General class licensees must also have passed the Technician written examination.
The Amateur Extra class license conveys all available U.S. Amateur Radio operating privileges on all bands and all modes. Earning the license is more difficult; it requires passing a thorough 50 question examination. Extra class licensees must also have passed all previous license class written examinations.
Source from ARRL