The problem with understanding prayer as conversation is that prayer is so much more than communication. Reducing it to conversation makes it simply mental activity–words and thoughts being a product of the left hemisphere of the brain. Prayer includes the mind, but is not limited to it. God invites engagement with more of our brain and more of our being. The glorious truth is that I can be praying to God without speaking to God, or without even consciously thinking of God. If this wasn’t true, how could we ever hope to realize the ideal of continuous prayer that is encouraged by the Scriptures (1 Thessalonians 5:17; Ephesians 6:18)? Obviously we cannot be thinking about God all the time. Nor can we be talking to God all the time. But prayer can be as foundational to our daily life as breathing. It can become a part of living, not just a religious practice or spiritual discipline.
A better starting point for an adequate understanding of the breadth of prayer is to view it as communion with God. Communion includes conversation but is much broader. Because it involves union, not just closeness and connection, it also entails much more intimacy than mere conversation. We are, as Paul reminds us, in Christ, just as Christ is in us. That language reflects the intermingling that is part of true communion. It does not get much more intimate than this–an intimacy that is based on the reality of a mystical union with Christ, in the present moment, not simply something to be hoped for in the future. Our experiential knowing of this reality may be limited. But the union is real, even now. And the communion that we experience in prayer is also real–so real that, more so than anything else that I know of, this prayer communion has the power to transform us from the inside out.David Benner, Opening to God: Lectio Divina and Life as Prayer (Expanded Edition)
That pretty much nails it.