Being more specific: the remote control will send a pulsed beam of infra-red light from and LED, usually rapid pulses (around 36KHz - 40KHz) interrupted at a slower rate to carry the necessary data to the receiver. The pattern of turning the rapid pulses on and off conveys the data.
The photodiode in the receiver can operate in one of two ways, either producing a tiny voltage when the IR light falls on it or changing conduction when light falls on it. Either way, after suitable amplification and filtering to remove the high frequency pulses, the original data can be recovered.
The high frequency is used because it allows easy electronic filtering, without it there would be too much random IR light from other sources which would interfere with the data.
Brian.