Layouts are the base of the theme, through which all templates are rendered.

Layouts are Liquid files that allow you to include content, that should be repeated on multiple page types, in a single location. For example, layouts are a good place to include any content you might want in your <head> element, as well as headers and footers.

You can edit the default theme.liquid layout, or you can create multiple custom layout files to suit your needs. You can specify which layout to use, or whether to use a layout at all, at the template level:

Diagram of theme architecture components with the layout highlighted.