For the present, we shall simply explain the quality of these persons that in the Catholic vocabulary are called mystic. Mystics are holy persons who have reached Christian perfection. They are no longer beginners, proficients. They may, of course, still grow in virtue. But their main concern is to remain united with God.
Mystics are gifted contemplatives.
We must carefully note that a person can be very holy and pleasing to God without being a gifted contemplative. On this level mystics possess what is called infused contemplation. The most authoritative description of a mystic as a gifted contemplative is given by St. Teresa of Avila in her masterful work, The Interior Castle. The description is given in the 4th to the 7th mansions of St. Teresa's description of infused contemplation. Mystics may finally be persons who manifest charismatic phenomena.