can anybody tell me that what is difference between Synchronous Limit and asynchronous Limit in soql governor limit in apex?
Synchronous means calling the apex class using Visualforce page, Trigger, Execute Anonymous of dev console. These type of call hold the process until they complete and run in main transaction thread.
Asynchronous operations are calling apex using batch, Future methods. These process run in background and don't affect the main transaction thread. They run is separate independent thread with their independent governor limits from main transaction.
For both cases SOQL Limit is 50,000 records per transaction.