Hi there,

The process of superimposing the information content of a low frequency baseband, modulating signal on a high frequency carrier signal by altering it's characteristics ( amplitude,phase and frequency) is called modulation. Following bare the needs of modulation:

1) reduces the height of antenna

2) increases the range of communication

3) avoids missing of signals

4) allows multiplexing of signal

5) improves quality of reception

Hope it helps!