Prayer is a single word covering several distinct activities. Traditions that classify them tend to arrive at similar categories while disagreeing sharply about which matters most.
Petition is the most visible form
Asking for something is the form most readily recognised from outside, and it is the one that discussions of prayer usually take as the standard case. Arguments about whether prayer works are almost always arguments about this form alone.
Devotional literature often treats it as the least advanced form while defending its legitimacy, on the grounds that dependence is a real feature of a person's situation.
Instructions commonly address what may be asked and in what spirit, which is where traditions differ from one another most noticeably.
Thanksgiving and praise change the direction
Gratitude and praise are not requests, and they are frequently placed before petition in liturgical orders so that asking is not the first thing done.
The sequencing is deliberate. Beginning with acknowledgement is understood to set the relationship in which any later request is made.
Praise is often distinguished from thanksgiving on the grounds that it concerns what something is rather than what it has provided.
Confession has a structure of its own
Prayers of confession involve naming, acknowledgement and a stated intention, and many traditions attach specific forms and occasions to them.
The structure resembles other practices of accounting, which is why written examinations of conscience appear alongside spoken confession in several traditions.
Where confession is communal, the wording is usually general enough for a whole assembly to say, which changes its character considerably.
Contemplative prayer moves away from words
Traditions with a contemplative strand describe forms in which speech and even explicit request recede, leaving attention without content.
These practices are typically taught after the verbal forms are well established rather than as an alternative to them for beginners.
Descriptions of them are notably reticent, and writers in these traditions often say directly that the vocabulary available is inadequate to what is being described.
The categories are ordered differently
Some traditions treat petition as the foundation on which everything else rests, while others treat it as the elementary form a practitioner is expected to grow out of over time.
Where a tradition places contemplation likewise varies, from the goal of the whole practice to a specialised vocation for a few.
Knowing which ordering a given tradition uses explains most of what looks like disagreement about prayer between people describing the same activities.