Who is a Scrum Master? And what does he/she do?
A Scrum Master is someone who promotes and supports the usage of Scrum within the team.
He/She understands the theory, practices, rules and, values of Scrum
He/She ensures that the team follows the values, principles and, practices of Scrum
They remove any distractions and impediments that hamper the progress of the project
The Scrum Master ensures that the team delivers value during the sprint