Licensed therapists have to conform to a recognized standard in ethics and methods around psychotherapy. There are then different types of specialties/theories that build atop that base framework.

Psychology (like medicine and computer-science) is an ever evolving science. Just 50 years ago, we would try to shock the depression out of you - and it worked for a short period of time.

We haven't reached the final say in how the mind works, or who we are, and we probably never will, but every year we get closer.