In reply to mitesh.patel:
As far as I get your question, here is my guess in its explanation. Binding is like instantiating some entity inside some other module without changing the physical code of the parent module.
If you don’t specify module instance in bind statement, then the bind will apply to all the instances of parent module.
bind DUT Assertion_module myassertion(.*) // This will bind to ALL the instances of the module "DUT"
bind DUT:inst Assertion_module myassertion(.*) // This will bind to only "inst" instance of the module "DUT"
Refer to this pdf for more information.