Liquid is an open-source template language integrated into portals. It can be used to add dynamic content to pages, and to create a wide variety of custom templates. Using Liquid, you can:
Add dynamic content directly to the Copy field of a webpage or the content of a content snippet.
Store source content by using web templates, entirely through configuration within Power Apps, for use throughout the Power Apps portals content management system.
Render a website header and primary navigation bar, entirely through configuration within Power Apps.
Note: page is one of the available liquid objects.
Reference:
https://docs.microsoft.com/en-us/powerapps/maker/portals/liquid/liquid-overview
https://docs.microsoft.com/en-us/powerapps/maker/portals/liquid/liquid-objects#page