Definition: «is an important vehicle for meaning. It helps the listener get a clearer picture of what a speaker intends to mean» (McCarrigan, Nitter Rugsæter, page 215)
Intonation is important when you speak to strangers to be polite and when you listen to people to understand exactly what they mean so you can be able to understand the whole message not only some pieces and fragments of what they are telling you.
The meaning of what a person is saying can change with the tone, if it goes up or down. This is a quite good example:
In teaching intonation to children it’s important to make it simple as possible for them to understand by using examples and repetitions. You can lower and higher the tone when you speak to them and make some phrases and write them down on the smartboard or blackboard in the classroom.
Desmond McGarrighan, Kåre Petter Nitter Rugesæter. 2018, Fagbokforlaget. Chapter 29.