The Website area is where you manage the building blocks of your site. Where pages and posts hold your content, the Website area holds the templates that content is poured into, and the files shared across it.
To open it, click on CMS in the main navigation menu, then open Website.
Templates
Templates define the layout a page is built from — the sections a page has, and therefore the fields you fill in when you edit it. Each template has its own CSS and JS, so a template carries the styling and behaviour it needs.
You can preview and validate a template before using it, so you can check it renders as expected and catch problems before any page depends on it.
Changing a template changes every page built from it. Preview and validate first, then check a page that uses the template.
Files
Files are the shared assets used across your site — the things more than one template or page needs to reference. Manage them here rather than uploading a copy for each page that uses them. 
