In the UK, usually a practitioner is either a psychologist, or a psychotherapist. The two paths of training are quite different, and the aims of treatment are also different.
A psychologist will usually work in a clinical setting, like a hospital. They can diagnose, and work with, severe mental health issues, and are more 'scientifically' based, often using cbt.

A psychotherapist focuses much more on a relationship with the client to look at emotional and behavioural issues, and use the therapeutic relationship as a vehicle for change.

Both totally have their valid place in healing, and they're both different.

Hope this helps a bit...