Psychologist covers a broader topic.
If you mean clinical psychologists, that's backwards. Psychotherapists can be psychologists, social workers, psychiatrists, psychoanalysts, or even pastoral or spiritual counselors. I fact, no state that I know of (in the USA) has any legal requirement that a person needs any educational credential at all to publicly advertise herself as a psychotherapist.
On the other hand, there are non-clinical psychologists in academia, business, and other settings. So which one is broader depends on the context.
The difference: psychologists, whether they do psychotherapy or not, have a graduate degree in psychology from an accredited institution of higher learning. Psychotherapists, whether they have a degree in psychology or not, do therapy (healing) of the psyche (mind). Generally, psychotherapy refers to "talk therapy" of one kind or another, rather than to medication.What do I talk about with the psychologist?
What he said. To add to that, a psychologist actually need a doctorate. Social workers, mental health counselors, etc, can also do therapy, but to call yourself a psychologist in the U.S. you must have a doctorate degree. It doesn't actually have to be accredited. And you can actually be a psychologist without being licensed to do therapy. It gets technical, but what Hayyim stated kinda summarizes it up. If you want more details, feel free to ask.why do I have two different lumps on the lip of my vag?