Modulation is a process to transmit the message along with the carrier signal. i.e. In the modulation process we convert the analog signal to Digital one and vice versa. As Data communication needs the digital quantity and signal so modulation process is helpful for data communication.
Modulation is the process of converting analog to digital and vice versa. When the data is converted it is transmitted over that particular medium. Example:Voice is analog signal converted to digital (bit "1" "0").