Hello Anurag,
The Test.isRunningTest() method is used to identify, if the piece of code being executed is invoked from a Test class execution or from other artefacts such as a Trigger, Batch Job etc. Returns true if the code being executed is invoked from a test class otherwise returns a false.
! is the Logical complement operator. Inverts the value of a Boolean, so that true becomes false, and false becomes true.
So, (!test.isRunningTest()) will Return false if the code being executed is invoked from a test class otherwise returns a true.
Thanks.