A scrum master is one of three fundamental roles in scrum methodology. Scrum masters serve to facilitate both product owners and the team. They neither have management authority, nor can they commit to work on the team's behalf.
A scrum master may also be referred to as a servant leader.
Techopedia explains Scrum Master
Scrum is a framework for project management often used within software development environments.
Scrum methodology is facilitated by a scrum master, a major role in the scrum methodology. The scrum master is accountable for removing disorders so as to produce sprint deliverables. The scrum master acts as a buffer between the product owner and team, ensuring that the scrum process is used as intended. Scrum masters also enforce scrum rules within the scrum.
The key role of a scrum master is to protect the team and keep its members focused on tasks. Scrum masters also help product owners maximize productivity by maintaining the backlog and release plan, thereby informing product owners about the scrum team's success.