SERAPHIM are associated with love.
CHERUBIM with keen intellect and insight.
THRONES with tranquility.
DOMINATIONS represent the universal sovereignty of our Creator over all things; and their chief virtue is zeal for God's authority, and zeal that all peoples acknowledge the authority of Christ Jesus, the King of kings.
PRINCIPALITIES are guardians of entire nations and of very important
people.
POWERS  represent that attribute of God by which "He orders all things sweetly" (Wisdom 8:l).  The Powers give us an example of strength in meekness, a quality that the martyrs of the Church possessed.  They enlighten the lower choirs of angels as to HOW things ordered to be done should be accomplished.  St. Gregory said that the Powers plan and direct the campaign against the legions of darkness who wage spiritual warfare against people in the world.
VIRTUES characterize immovable strength, or enthusiasm in a work to be accomplished.  To the Virtues is generally attributed the regulation of the weather.  With confidence people pray for their aid during times of drought or severe storms.
ARCHANGELS  are entrusted with the more important messages to human beings.  The Archangel MICHAEL led the battle in heaven and cast out the rebellious fallen angels who were led by Lucifer and became devils.  The Archangel RAPHAEL accompanied young Tobias in travel, and proposed cures for his bride and father, so he is invoked by travelers, the sick, and the young leaving their family home for the first time.  The Archangel GABRIEL delivered the greatest message of all time:  that God would assume human nature through the instrumentality of the Blessed Virgin Mary (Luke 1).  He is invoked as the patron of communicators and people involved in the media.
GUARDIAN ANGELS are the ordinary messengers and guardians of children on earth.  Their characteristic virtue is humility.  You may recognize this as a prayer many of us learned as children:  O Angel of God, my guardian dear, to whom God's love commits me here, ever this day be at my side, to light, to guard, to rule and to guide.

Though we are not strictly bound to believe that a particular angel has been assigned to each human individual, still, since the doctrine of
Guardian Angels has always been taught in the Church and many passages of Scripture support it, why deny it?  Even the patriarch Jacob proved his belief in Guardian Angels when he imparted his deathbed blessing on the sons of Joseph:  "The angel that delivered me from all evils, bless these boys"
(Gen. 48:16).

Indeed, Angels are among our friends.  In 1916 the "Angel of Portugal" appeared to three little children, Lucia, Jacinto and Francesco and taught them how to pray with attention and to do penance on behalf of sinners. Thus he prepared them to hear and obey Our Lady of Fatima, Mary,  Mother of Jesus, who appeared to them later with messages for the entire world.
Our Guardian Angels carry heaven with them and teach each of us its
language.  The angels are near to us when we worship God together as is mentioned several times in the Catholic Mass.  All know the Christmas song of the angels, "Glory to God in the highest." (Luke 2:14), as well as their "Holy, Holy, Holy" (Isaiah 6:3; Revelations 4:8).  Every day, as we are invited to pray with the angels and to invoke their aid, we also need to thank them for never abandoning us, even when we forsake them.