1) The document discusses the priesthood of Jesus Christ and how he serves as a high priest in heaven.
2) It contrasts the old Mosaic covenant with the new covenant established by Jesus, arguing that the new covenant is superior because it completely forgives sins and requires a perfect sacrifice in Jesus.
3) The new covenant will make the old covenant obsolete, as God's laws will be written on people's hearts rather than on tablets of stone, and people will truly know God rather than needing to be taught.