A main aim of a dissertation is for you to show you can independently sustain a piece of high level work. This is your activity and your responsibility, although you will have guidance and support from a supervisor. Co-supervision (where 2 tutors share you) is unlikely at Master's level.
The working relationship between you is important. All supervisors have their own personal style; some choose to be more formal, while others prefer a more personal relationship. You'll need to discuss how you will work together.
You may also work alongside your peers, either as a formal group (e.g. Learning Set) or as a less formal peer support group.
Your working relationships with others, and the feedback you get from them, are important to producing your dissertation. This section covers: