Ursa, as a Mormon I can assure you that we are Christians, in that we fully accept the divinity of Christ, which I would be consider to be the defining characteristic of Christianity (likewise, we also fully accept the divinity of the Holy Ghost or Holy Spirit.) We are not, however "traditional Christians", in that we reject the Creeds entirely. So under the broadest hierarchy, we would not be "Catholic", or "Orthodox", or "Protestant", but something like "Christian/Other".
1) As Mormons we accept the Bible as scripture, but reject "sola scriptura", as we consider living prophets and apostles to have authority equal to that of scripture, and we have an open canon (which is to say that we add scriptures to the canon as they are accepted by the Church as inspired.) The prophets and Apostles in ancient times claimed a level of authority equal to that of the Law given by Moses, and the living prophets and apostles who lead our Church claim a level of authority equal to that of the Bible.
2) We understand the importance of authority to administer the ordinances (or sacraments), but do not consider the Roman Catholic Church's authority to be valid, as the Apostles, not the Bishops, hold the ultimate authority, as they did in ancient times. The ancient Church, not necessarily through any fault of its own, lost its authority after the s of the Apostles.
3) As Mormons, we understand the importance of both faith and works, including personal worthiness, service to others, and the ordinances (or sacraments), as being important for salvation. But salvation ultimately comes through Jesus Christ, and is given as a gift to those who have followed His commandment to follow Him.