Layouts and templates are used for creating classically rendered websites.
Layouts contain general markup that is shared across the pages and collections where the layout is set.
Templates contain markup specific to a page or collection.
Page Templates contain html and Page Propellers code that renders page content.
Collection Templates contain html and collection propellers code that renders collection items content.
An email is sent to the Admin Email(s) specified in Airship CMS whenever a public post is created for a collection with "public make" enabled. Emails are also sent when eCommerce transactions occur (creating Orders, Invoices, Subscriptions, and Shipments). See Airmail Email Templates for more information.
If you are building a single page application, you probably only need a template that loads on the root url for the SPA. In Airship CMS, you can set which pages should behave like a SPA. (Documentation coming soon).