A carrier frequency is a technical term used to describe a frequency that is generated by a transmitter such as a radio or radar transmitter. A carrier frequency is sometimes known as a resting or center frequency.
Carrier frequencies are fixed frequencies that have been designed or altered to carry data. This type of frequency is measured in Hertz and only carries information, hence the name. The size of the frequency doesn't change after modulation and the signal is generally symmetrical before and after modulation. Carrier frequencies are used in telecommunications, and others are used in radio and in other analog and digital applications.