What is the syntax for calling function with [] in jQuery

What is the syntax for calling function with [] in jQuery

Hello all,
 
I have seen the following methods to call a function in jQuery.
 
  1. Case 1: $.validator.methods[method].call
  2. Case 2: $.validator.methods[method](parameter1)
           
            Where can I find the reference document for the usage of [] to call a function in jQuery.
             
            Thank you