As it is stated at w3schools in jQuery tutorial:
$(selector).action()
From a theoretical point of view .action() is a jQuery method or a jQuery function ?
As it is stated at w3schools in jQuery tutorial:
$(selector).action()
From a theoretical point of view .action() is a jQuery method or a jQuery function ?
 
    
    $(selector) is a jquery object who represents DOM element, so .action() is a method. 
