Cellphones are like sophisticated radios, with microphones and wireless antennas. When a cellphone user speaks into the microphone, the voice wave is converted to an electrical signal, which is transmitted as a radio wave to the receiving phone and then reconverted to an electrical signal and then a voice signal.
As cellphones have relatively compact antennas for portability purposes, they can only send signals over a very short range. To solve this problem, cellphones are connected to wireless networks, which operate on grids. Grids split regions or cities into smaller cells, with each cell covering a few city blocks or up to 250 square miles.
Each cell has a base station. Each base station has a mast and other radio equipment. The masts link cellphone users to local telephone networks, the Internet or other wireless networks. Cellphones don't directly interact with each other; they make use of the masts. For instance, a call from cellphone A first goes through a mast A and a base station, then to a mast B and another base station, before the second cellphone finally receives the call. Cells solve the challenge of few available radio frequencies, as cellphones in different cells can make use of the same frequencies.