Synchronous operation

It is a technique to process multiple threads (methods) at about the same time. It is processing in a particular way in which the execution start-up of the next process depends upon the execution completion of the previous process in the scheduled process list.

Asynchronous operation

In this technique, execution of a process or thread remains independent from other processes or threads which are set for asynchronous behavior.

For example, what if the computer schedules thread A and thread B to process in order within a single CPU environment. Say thread A has a very complex logic and takes 30 seconds to finish. In the synchronous operation, thread B has to wait for 30 seconds to get its turn. But if thread A has been implemented to run asynchronously then thread B will not require waiting for 30 seconds. B will get his turn in about 1 second. Yes, the fact behind this is that A will anyway take 30 seconds or may be more for its execution.