Pages
Pages are very simple to create. Any JavaScript file with an export should create a new page within Gatsby. Hot tip: use a underscore (_) to have that file ignored. Manual file creation is just one way of creating new pages though.
Sources
We can use any number of sources to grab content from all over the web and use that content to create new pages. Examples of sources might be a content management system (CMS) like Wordpress or Prismic, or more non traditional sources like Airtable.
Templates
Generated pages uses templates to display their content. Templates are assigned for each page type. A template can be configured to display content from a source on the web or an internal piece of data like a markdown (.md) file or JSON. There's a lot of flexibility available here.