There is essentially no difference between counselling and psychotherapy. The definitions are arbitrary and change depending on who is defining them. I originally distinguished them as being short and long-term but my view of the definitions have changed in the past year.
Traditionally, the term psychotherapist was reserved for psychiatrists (doctors specialised in mental illness) who had further trained in psychoanalysis. In the 1950s in the USA Carl Rogers was developing person centred counselling. He coined that term because he wasn’t allowed too call himself a psychotherapist, despite being a medical doctor specialised in mental illness.
The profession is not regulated in the UK and there are many different types of counselling and psychotherapy training and modalities. This can make it confusing for a person looking for a therapist. I have tried to address that in this blog post.