Meditation differs from prayer, even from silent prayer, in that meditation is thought about God and contemplation of His word and His works.
Meditation normally begins by reading from the holy Scriptures, the Word of God. This is called in the spiritual tradition lectio divina. It is the slow and attentive reading of the Bible, or perhaps the writings of the church fathers and saints, not for the purpose of gaining information, but for the purpose of communion with God.
Such meditative reading may be of the sort where the person tries, with the power of his thought and imagination, to enter into the event about which he is reading in order to become its contemporary participant. Or, it can be of the sort where the person merely reads and listens in silence, without imagination or rational thought, in order to let the Word of God enter his mind and heart in order to remain there, to bring forth its fruit at the appointed time.
Psalmody, done either alone or in the churchly assembly, exists for this latter purpose. When reading or chanting the psalms, the person does not try to think about each word and phrase. Rather he cuts off all reasoning, and opens his heart to the Lord, uniting “his mouth with his mind,” (St Benedict) and allowing the Word of God to be planted within him to blossom in his soul with the fruits of the Spirit. This also is the case with churchly hymnology. It is sung for the glory of God and the edification and expansion of the soul through the contemplation of the Lord in His words and works of salvation, much more than for any intellectual instruction. This type of meditation is especially advised in times of despondency.
There is also the type of meditation and contemplation done totally in silence, without any words or images or thoughtful activity at all, not even psalmody. The person merely sits in silence, often in the presence of holy icons, and emptying his mind of all thoughts, imaginations and desires, listens to God in silence, the divine “language of the Kingdom of heaven.” (St. Isaac of Syria) This type of meditation, for a person of unceasing prayer, will be the “prayer of silence,” with the “bubbling spring” of the Jesus Prayer as its only foundation and background. In such contemplative prayer and prayerful contemplation, the spirit of man becomes one with the Spirit of God. (cf. I Corinthians 6:17)