When you run a dialogue, you can start it from any Label rather than from the top, if you want.
But what if you have a set of initial variable state that you want to always be set up, regardless of where the dialogue starts from?
Headers exist to solve this problem. Headers must be declared at the top of a script, and are enclosed by lines with 3 equal signs:
===
[set NumberOfWishes 3]
===Only set lines are allowed in headers.
Headers are run when dialogue is created, before you call Start. This is to
allow you to override variables that are set in the header before calling Start
if you wish.