Prayer is communicating with the Divine. Sounds overpowering and simple. Most often, we think of prayer as talking to God. However, the end result of prayer is listening to God, as the Lord is speaking to us and we are on a life-long journey to seek the source of our existence, who has revealed himself to us as God the Father.
The highest form of prayer is the Holy Sacrifice of the Mass. In this liturgy of the Church we enter into the presence of the Triune God through the paschal mystery of Jesus Christ. The Paschal Mystery is the life, death, and resurrection of Jesus Christ. The entire purpose of the Church is to know Jesus Christ--the reality of Him, to experience Him. Jesus, in turn shows us the Father. All of this through the power of the Spirit.
Prayer for a Catholic is allowing the Holy Spirit to work freely in us to show us Jesus Christ, the Incarnation of God.