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 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.
Psychologist covers a broader topic.
