WHat is a representation? What criteria have to be met to call sth. a representation?

WHat is a representation? What criteria have to be met to call sth. a representation?

Representation is a hypothetical internal cognitive symbol that represents external reality, or else a mental process that makes use of such a symbol; "a formal system for making explicit certain entities or types of information, together with a specification of how the system does this.". Mental representation is the mental imagery of things that are not currently seen or sensed by the sense organs. In our minds we often have images of objects, events and settings. If we were asked to recall particular events from our past we would be able to see the people, remember the places or even feel the smells that were present there, even though we are not currently smelling them.
I'm not sure whether I get the second question right, but according to the textbook to call sth a mental representation we have to have some sort of simulation of a presented actions and objects that appear in the story. When we read about kicking or moving our fingers certain brain areas responsible for these kind of movements get activated as if we were actually moving e.g. our fingers. Our minds represent the actions and act as if we were performing them (of course this activation is to much lesser degree than when we actually perform some actions).