What's the difference between synchronous and asynchronous communication?

Synchronous communication requires clocking mechanism between communicating devices. One side will be a master and the other receiver of clocking pulses. Asynchronous communication does not require clocking. Both communicating devices can send data independent of each other and without waiting for any synch pulses. Serial ports can either be synchronous or asynchronous. Synchronous COM ports will require extra pin or wire to be connected between devices for clocking signals. 

Synchronous Communication means the communication is matching the current situation or operation and related to the operation in the time being, but asynchronous communication means the type of communication that wasting time and not the related to the current operation or business case