About half of psychologists are clinical psychologists, or clinicians. The other psychologists are research psychologists, although they may have jobs in several different fields, where research is not the primary focus of their work. Clinical psychologists may also be researchers, but research psychologists cannot be clinicians. The relationship between clinicians and research psychology is similar to the relationship between medicine and medical research, and between engineering and physics. Clinicans are applying psychological knowledge, just as medical doctors are applying medical knowledge, and engineers are applying physical knowledge.
Clinical psychologists differ from psychiatrists in two important ways.
One, their training is different. Clinical psychologists have PhD degrees, which includes doing independent research, as well as coursework and practical training. Psychiatrists do coursework as well as practical training, but they do not have to do any research. There is quite a debate about whether the rules should be changed so that clinical psychologists can prescribe drugs. If more people can prescribe drugs, then more incorrect prescriptions will be made simply because of human error.