The BACP Ethical Framework defines supervision as:
"A specialised form of mentoring provided for practitioners responsible for undertaking challenging work with people. Supervision is provided to ensure standards, enhance quality, advance learning, stimulate creativity, and support the sustainability and resilience of the work being undertaken."
Supervision offers you a reflective space in which to develop practice and so benefits client safety. All aspects of your practice should be open to supervision.
Its a very good question. Supervision is so much more than just chatting about your clients and making sure that you are working ethically. It's all about you and how you are working. There are many different models of supervision that you may have heard about. Carroll's, The Seven Eyed model and more. All of them include space for you to explore, educational links an collaborative work.
HINT: Don't be fooled by supervisors advertising themselves as a 'person centred or CBT' supervisor!
There is no such thing. Its all about the model they use. Ask them!