When to use utf8 as a header in py files

Question

Some source files, from downloaded code, have the following header

# -*- coding: utf-8 -*-

I have an idea what utf-8 encoding is but why would

Answer 1

When you use non-ascii characters. For instance when I comment my source in norwegian if charachters ØÆÅ occur in the .py it will complain and not "compile".