Templates
Use Templates to control the surrounding layout for Pages, Posts and listings.
A Template provides the page shell around normal content. It is the right place for shared layout structure that should not be copied into every Page or Post.
Default Templates
The site has default Template choices for normal Pages, Posts and archives. Resource Packs can provide defaults, and Site Settings/Core Defaults can be used to select published replacements where supported.
Per-content Template
A Page or Post can choose a different published Template when its layout genuinely differs from the site default. Use this sparingly; a small set of clear Templates is easier to maintain than a different Template for every Page.
Preview changes
Use Resource preview or content preview before publishing a changed Template. A Template can affect many routes at once, so check at least one Page, one Post and any special content type that uses it.
When to use a Component instead
If you only need a reusable block inside an otherwise normal Template, use a Component. Keep the Template focused on the overall document structure.