Liquid is an open-source template language integrated natively into Power Apps Portals. It basically acts as a bridge between the Common Data Service data and the HTML or text output sent to the browser. It can be used to add dynamic content to pages, and to create a wide variety of custom templates. It is secure, as it only provides access to the data and operations explicitly allowed by Power Apps Portals.
Dynamics 365 CE, Logic App/Flow, Power BI, Portals