In this website, references to 'therapy' cover Counselling & Psychotherapy.
There are various types of mental health professionals and they can be easily confused. There are varying views of what psychiatrists, psychologist, psychotherapists and counsellors do, and various ways of differentiating between them. I will therefore offer you my take on the field in the UK, and that in itself is subjective.
In general the difference between psychiatrists, psychologist, psychotherapists and counsellors is in the type, orientation and duration of their training. Like any other profession, the individual has a key part to play, and key in choosing a practitioner is personal fit. It is advised to ask and check which body a practitioner is registered with.
Counselling & Psychotherapy training are similar in terms or orientation and training and Counselling tend to have a shorter training process then psychotherapy. Practitioners are required to undertake therapy themselves as part of the training and the training tends to be practice orientated with an increased emphasis on academic qualifications and research. Counselling process is usually focused on specific problem or issue whereas psychotherapy tends to evolve from counselling, is longer term and covers a wider scope.
Coaching is often used in performance related environment such as business, sports and the workplace and tends to be about achievement although there is a growing number of “life” coaches who apply a similar methods to personal related goals. Training duration can significantly vary, the coaching process can vary from a one off session to short term work and the field is relatively not regulated.
There are various types of psychologist (eg. clinical, behavioural) and they have a chartered status. Psychology training is mainly through an academic and research route and tends to follow the medical and behavioural model. To my knowledge, Psychologist training does not require the psychologist to undertake therapy themselves, with the exception of counselling psychologists, who in orientation are closer to counselling and psychotherapy.
Psychiatrists are medical doctors who specialise in mental health, in the same way that other medics specialise in liver, heart or children. They can prescribe medication and normally tend to work with the severe spectrum of mental health.