The next form of prayer is meditation. St. Teresa of Avila does not separate these forms (oral prayer and meditation) for when one is saying oral prayers he should certainly meditate on what he is saying. He should know to whom he is addressing and what he is asking for, and to whom he is asking. [Interior Castle p. 32]
The Catechism of the Catholic Church says that it is a quest, a person trying to understand and respond to the life asked of him by Jesus Christ. The best way to do this is by reading scripture, especially the Gospels, by looking at holy icons, by reading the Church Fathers and other spiritual writers. One does this to come into the light: "Lord, what do you want me to do?" Christian meditation should go further: "to the knowledge of the love of the Lord Jesus, to union with Him" [#2705-2708].