Subtemplates help you save time. Sections that should look the same everywhere on your website, like the head or footer, are easier to manage if you create them as subtemplates.
Head and footer are the most common sections to use subtemplates, but you can also use them for other regions in your html code that you want to be consistent throughout your website.
To create a subtemplate you just need to tick the box below the source code editor when creating a new template.
IMPORTANT: For subtemplates you only need the content of the tag. The tag itself in the original template remains intact. You just need to refer to the subtemplate like you can see in the example below.
The subtemplate will then show up in the template overview.
Use the data-sub-template attribute and an ID to insert the subtemplate into the HTML of your template, like this: