T's definitely use what they learned in school in the room with you. Some T's more than others. In school T's learn a lot of things! It's really really complicated, and a lot of it doesn't translate to therapy itself but provides the groundwork (i.e., cognitive, developmental, etc), but here is the stuff that is relevant to you:

They learn a whole lot about theory in their classes, and they learn about how to practice therapy, too. T's start by role-playing therapy with other T's-in-training. Then they go on to practice by treating clients with mild problems (who know they are seeing a T-in-training). In time they start seeing harder cases. Their tapes are watched by their supervisors who tell them what they're doing right and what they're doing wrong. The supervisor keeps an eye on them like this for a while. Then T's don't tape their sessions anymore but still go and talk to supervisors. T's have to have supervisors until they have a license. They learn a lot in supervision which is a big part of T training. This training with supervisors tells T's how to implement the theories and the different things they learned in their classes. When T's say, "You must feel really alone right now," they probably learned this from experience with other clients like you. In classes, they might also learn useful metaphors, and maybe even some complicated techniques like EMDR. They learn particular ways of doing therapy, which may start out sort of scripted, but end up coming naturally to the T and they will use their own words then.

They also learn about diagnosis and how to treat the different diagnoses they might run into. Like they will learn how to spot OCD, or PTSD, or bipolar, or what have you, and they will know the right course of action to take. Like they will know that if you are bipolar they should refer you to a psychiatrist to get on some mood stabilizers. Or they'll know that if you have OCD you should probably be getting exposure and response prevention therapy and if they don't know how to do it, they will refer you to someone who does. Just examples of the many things they learn how to do. They learn how to deal with each case they run across.

T's also learn about research in school. They learn about it so they can keep up with the new ideas that are changing the way therapy is done, or the way we view certain diagnoses, and other things.

T's also learn how to do testing. Like IQ tests and learning disability tests and other things. Depending on their school they might have learned other things as well, like how to use an fMRI machine for example, and how to interpret fMRI results and other neuropsychological testing.

As far as what makes T work, I think farmergirl is spot on (although I have some complicated research questions about how/why therapy works, but that is something we will know in the future when I change the world! )