"Those who are versed in ascetical and mystical theology are well acquainted with the different categories of human relationships with God: prayer, sometimes restricted to vocal prayer; meditation; contemplation; and the prayer of quiet.
Prayer in general is an elevation of the mind to God in order to converse with Him.
Vocal prayer is any form of prayer which is expressed in words, whether written or spoken.
Meditation or mental prayer is the application of the mind to some supernatural truth (e.g., the life, passion or death of Our Lord, His teachings, death in general, destiny of the soul after death, etc.) in order to penetrate its meanings, love it, and carry it into practice with grace; all these aim to promote God's glory and our advancement in virtue.
The next plateau in spiritual advancement is contemplation, which is defined as a simple, loving, protracted gaze on God and divine things through the gifts of the Holy Ghost and a special actual grace which takes possession of us in a passive manner.
The prayer of quiet is an advanced type of contemplation in which the soul experiences an intimate awareness of God's presence that fills the soul with an ineffable sweetness and delight.
Contemplation and Prayer of Quiet are usually listed under mystical theology and the first two under ascetical theology."
From the book, "A Spanish Mystic in Quito , Sister Marianna of Jesus Torres"
By Monsignor Luis E. Cadena y Almeida, page 35 & 36.