#1 The team – who owns the sprint backlog and are responsible for estimating. functionality and fulfilling the commitment made at sprint planning meetings.
#2 The Product owner – who owns the product backlog and decides on product functionality.
#3 The scrum-master who owns the impediment log and is responsible for removing any blockages that hinder the team from performing and fulfilling their commitments.
I tend to view the different roles in scrum as an allegory to help me consolidate the lines of demarcation:
#2 The product owner(s) are the fans – who pay to attend concerts, pay for the music and therefore ultimately determine what music is popular and what music the band plays.
#3 The scrum-master is the bouncer cum manager – they protect the band from over enthusiastic fans, make sure that no harm comes to them – book the gigs and makes sure that the band turns up on time.