What is Modulation? Explain in brief.

Hint: In telecommunication the process of encoding some information in carrier wave by varying one or more properties of the carrier wave is known as the Modulation. In the 20th century mostly used modulation procedures were Amplitude modulation (AM) and Frequency modulation (FM).

Complete step-by-step answer:
When some information signal is needed to transmit from one place to another, the main problem arises is to properly separate it from the noises present in the ambience. To resolve this issue modulation procedures are used.
Amplitude modulation (AM): In amplitude modulation the amplitude of signal strength of the carrier wave is varied depending on the amplitude of the original signal. For AM the frequency of carrier waves is generally used quite higher than that of the signal. After modulation the carrier wave frequency remains the same as before just the amplitude gets modified depending on the signal. So this process is known as amplitude modulation.
Frequency modulation (FM): In frequency modulation the original signal is superimposed with a very high frequency carrier wave in such a way that its frequency gets modified according to the amplitude of the original signal. So, after modulation the frequency of the carrier wave varies within some fixed interval known as the bandwidth of the signal. But throughout the whole signal the amplitude remains constant as that of the carrier wave.
Apart from AM and FM, there are various other modulation procedures also. They are Phase modulation (PM), Space modulation (SM), Single-sideband modulation (SSB) etc.

Note: Although all the modulation procedures are used to reduce noise inside the signal, FM has the best signal to noise ratio for all types of manmade interference. As the bandwidth of FM is higher than AM signal the quality of sound is better in FM. Also, transmitting signals through FM needs less radiative power compared to AM. However, FM signals are impacted by physical barriers.