TA is a logical way to  understand who we are and how we interact with others in the world. The cards can be used in therapy sessions to explain how TA works, as a prompt for the counsellor, or  the client can hold and look at an individual card to make the explanation clearer as the counsellor speaks. 
They can be used by individuals who have a basic knowledge of TA or those who are willing to look up an explanation of the concepts online. 
Those of us who love TA will find ways to use the cards to remind ourselves of this amazing system for understanding how we operate and how others respond.