Differentiate between synchronous and asynchronous types of serial communication.  

Serial data communication uses two fundamental types as, synchronous and asynchronous. With the synchronous communications, the two devices originally synchronize themselves to each other, and after that continually send characters to stay in sync. Even if data is not really being sent, a constant flow of bits permits each device to identify where the other is at any specified time. It is, each character that is sent is either an idle character or actual data. 

Asynchronous implies "no synchronization", and therefore does not need sending and receiving idle characters. Though, the beginning and end of each byte of data should be identified by start and stop bits. The start bit specifies when the data byte is about to begin and the stop bit signals while it ends. The requirement to send such additional two bits causes asynchronous communication to be a little slower than synchronous however this has the advantage that the processor does not have to deal along with the additional idle characters.