Kirby makes it possible to access any content in your content folder from any template with mostly just one line of code.
There are three main template variables, which are available in each template:
// contains everything about the site
// (title, description, pages, etc.)
// contains everything about the current page
// contains all pages of your site
You access stuff inside those templates in a very jQuery-ish way.
Please read more about it in the subsections about each variable.