The heart of prayer, I think, is soul to soul communication with God. This I believe is the very basis of prayer. Then, from this kind of prayer flows other forms or outlets of prayer, mainly petition. I also see, however, that conversational prayer flows out of it, confession of sin flows out of it, and praise and thanksgiving flows out of it.
The following Psalms suggests this idea of soul to soul communication with God:
To You, O LORD, I lift up my soul.
O my God, I trust in You;
Let me not be ashamed;
Let not my enemies triumph over me.
My soul waits for the Lord
More than those who watch for the morning–
Yes, more than those who watch for the morning.
Find rest, O my soul, in God alone;
my hope comes from him.
Now because the soul contains the mind, the affections, and the will, true prayer will involve all of these elements.
When we exercise our mind toward God as we meditating on the Word and on other good things (Phil. 4:8), the Holy Spirit is activated in our soul, and the life of Christ begins to flow in our blood.
When we meditate on the Word we also open the door of our soul to what is in our heart and to what is in the heart of God. Therefore, meditation on the Word also gives us that emotional connection to God.
Thirdly, in true prayer we use our will. With the will, when we listen to God, we choose to obey him. This obedience keeps the door of our soul open to His soul and keeps the life of Christ flowing to our soul. Moreover, by our obedience we prove our love to God, and He in return floods our life with His love and power (Jn. 14:21).
As I said earlier, from the prayer we are calling soul to soul communication will flow other kinds of prayer.
First of all, there is the type of prayer that is horizontal or earthly—having to do with our own needs on this earth. This would be the prayer of confession, and also of petition. The prayer of confession begins like this: as we are meditating on the Word and communing with God with our soul, the Holy Spirit makes us realize our sin. Accordingly, our regular prayers of communion turn to confession.
Likewise, here is how prayers of petition start: when we are having our soul to soul prayer time with God (as we are meditating on the Word) the Holy Spirit will use that precious time to help us realize what God’s will is and what our real needs are. Consequently, the Holy Spirit at that time begins to direct our prayers toward petition.
There are also the kinds of prayer that are vertical, or heavenly. These are prayers that are not about our needs so much, but rather about what God desires from us.
I think the grandest and the most selfless kind of vertical prayer is the prayer of praise. Some would not call praise prayer, but I would. It is the highest kind of prayer there is, a special kind of prayer. It is prayer that is only for God, not for us. It is prayer that we offer because we love Him; the kind of prayer that flows from a heart of love. We will naturally use this high form of prayer when our soul meets with the soul of God through meditation on the Word or perhaps through our meditation on the words of a song—when the Holy Spirit brings to our mind a truth about God or any of the mercies of God.
The prayer of thanksgiving is also a more vertical prayer, which I think is really a type of praise.
Another kind of prayer is conversational prayer. This is just plain talking to God and enjoying him. This kind of prayer I think should be used whenever we pray. It should be mixed in with our prayers of confession, our petitions, as well as our prayers of praise. This kind of prayer is not horizontal or vertical. It is that which links all types of prayer together. It is what makes our praying interesting and enjoyable. I think it could be termed the small talk of prayer, or the love talk of prayer, or even the intimate talk of prayer. It is the prayer that opens up the life and that gets personal and intimate. It is also the prayer of humor and silliness, which opens up the real self to God and likewise lets His healing touch enter the heart.
So this is what I believe prayer is in all of its outlets.