Tone is how you use grammar and vocabulary for different purposes, in different situations and with different people.
Your tone depends on if the situation is urgent or elective, if you are talking to a colleague or a layman, and if you are giving good or bad news.
Besides questions, requests and statements, other language functions include:
Informing (about facts)
Suggesting or recommending
Advising (stronger than suggesting)
Restating or explaining
We will review each of these.