Patterns?

Can anyone help explain how patterns work? I’m having trouble especially with modifiers for repetitions.
I’m looking at this article currently: http://www.lua.org/pil/20.2.html
And I am still having some trouble. Any help is appreciated.

like you can use . to work for any character, like:

the page has all the rules on there

How often do you usually need to use patterns?

Occasionally.