Sound signals can be transmitted by varying electromagnetic waves; this phenomenon is known as radio transmission. This is done via air and vacuum space, through which these waves pass. When these waves are delivered through an electric conductor, it can be transformed into various types of signals and sounds that transmit information.
The earliest uses of the radio can be traced back to sending signals for maritime in Morse code. These signals were communicated between land and ships. During the World War 1, radios were used for communication between the navy and armies. Today, radios are used for various other purposes, especially for passing on news and entertainment. Wireless networks, radio broadcasting and mobile communications are the most popular forms of radio used.
Audio uses - The radio can be used to transmit sounds in the form of Amplitude Modulation (AM) or Frequency Modulation (FM). FM radio is usually of higher quality and is not subjected to interference like AM radio. Most radio entertainment uses FM or AM. The aviation industry uses VHF AM, which enables the same channel from multiple stations. Marine radios use single sideband voice or narrowband FM like the police, government, commercial and fire services.
Telephonic uses - Mobile phones use different types of modulation systems to carry signals. While satellite phones use satellites.
Video uses - Radio is used for analog as well as digital television. Different modulations are used according to countries and the regional necessities.
Other uses - Radios are used in navigation, digital broadcasting, radar and heating. For navigation satellite transmits the position and time of its transmission, while radar helps determine the distance of object by sending out radio waves that bounce of these objects and comes back. Microwaves are a good example of how radio waves can be used to heat object. | 
