Traditional teaching, though not binding Magisterial teaching as far as I know, says there are nine levels or “choirs” of angels. The exact naming of these choirs varies by tradition. One version is, from highest to lowest: Seraphim, Cherubim, Thrones, Dominions, Virtues, Powers, Principalities, Archangels, and Angels.
Most of the names of individual choirs could probably be used to describe some or all of the others. For example, all of them obviously are angles, though only the lowest rank are given this as their choir’s name. “Archangel” could refer to any elite angel, regardless of whether they belong to the choir named “Archangels”. “Cherubim” is taken from the Old Testament and may or may not have originally referred to what we call angels at all, but tradition has assigned the name to the second highest choir. “Seraphim” is also of Hebrew Biblical origin and means something like “burning ones.” We say that they burn with love for God, but the word was also used by the Hebrews to refer to poisonous snakes (snakes whose bites “burn”), and through this we have the connection to Satan, who is often said to have been a Seraph prior to his rebellion against God. Other names, like Principalities and Powers, are taken from New Testament texts, often referring to demons which exegetes (or eisegetes, perhaps) have interpreted as angels who fell from these middle choirs.
Most of this does not have a great deal of bearing on an ordinary human being’s faith life. If the higher choirs have much influence on human affairs we know very little about it. Guardian angels on the other hand, who I’ve heard described as belonging to the lowest choir though I don’t know what the ultimate source is for that idea is, are clearly important due to their individual relationship with us. They protect and guide us throughout our lives, so it is good to remember and thank them from time to time.
