Prayer is the soul's sincere desire, uttered or unexpressed
Prayer can be a form of religious practice, may be either individual or communal and take place in public or in private. It may involve the use of words, song or complete silence. When language is used, prayer may take the form of a hymn, incantation, formal creedal statement, or a spontaneous utterance in the praying person. There are different forms of prayer such as petitionary prayer, prayers of supplication, thanksgiving, and praise. Prayer may be directed towards a deity, spirit, deceased person, or lofty idea, for the purpose of worshipping, requesting guidance, requesting assistance, confessing transgressions (sins) or to express one's thoughts and emotions. Thus, people pray for many reasons such as personal benefit, asking for divine grace, spiritual connection, or for the sake of others.
This Wikipedia entry points to a broad range of expressions of prayer; below are a number of articles written by reflect members and others on different styles of prayer they have found personally helpful.