First there is the Aaronic Priesthood. It is a preparatory Priesthood, meaning it is preparing the man in certain responsibilities and duties before he is ordained to the higher Priesthood, which we refer to as the Melchizedek Priesthood. Sometimes the Aaronic Priesthood is referred to as the lesser Priesthood. That doesn't mean it isn't as important. There are some vital ordinances performed by those who hold the Aaronic Priesthood including baptism, and blessing and administering the Sacrament. The offices in the Aaronic are deacon, teacher, priest, and bishop. Deacons, the "lowliest" of the offices are given the responsibility to pass the sacrament. I find this such a wise and sweet thing--it is an ordinance or renewal and remembrance for every single member. We all rely on that ordinance and need it so much. It is a great responsibility to give our young deacons such an important part of so great an ordinance. It teaches humility, patience, and respect for those served as well as for the ordinance and Whom it represents.
The Melchizedek Priesthood offices are elder, high priest, patriarch, seventy, and apostle. When our men are preparing to enter the temple/serve a mission, at some point they are ordained to the office of an elder. It is the "lowest" of offices in this Priesthood, yet it is the very same Priesthood that the Apostles hold. Honored and exercised in righteousness and worthiness, it is the same Power of God that can bless His children no matter what a man's office, calling, job, income, race, nationality, background, skill, etc. It is an equalizer that allows every man a chance to serve and be God's instrument in doing for His children what they cannot do for themselves, but which Power can be manifested through their faith.
I have a great respect for each office in both Priesthoods. I have been blessed to watch my brothers attain different offices as they have grown up. I've seen my father honor his Priesthood in his various offices. I'm now learning of friends who are being called to other offices of the Priesthood. I have greatly revered and followed counsel from higher Priesthood office holders who have been an integral part of my life--some of them (Presidents/Elders Hinckley, Faust, Maxwell, Wirthlin, Packer, and Perry) having been around for all of that life and have in recent times been passing through the veil to the other side. No matter their office, their duty, or their responsibility, I have been humbled and honored by every man who has honored or still honors his Priesthood.