This special nomenclature is called "Liquid" and it is a templating language invented by Shopify.
Card developers can use Liquid to combine both static and dynamic content in one Card design. The idea is that you build your Card with HTML and CSS (following our Design Guidelines) and then place certain tags within this markup where you want to dynamically populate the data that is returned from an API.
These Liquid elements in your Card's markup act as placeholders: when the code in the file is compiled and sent to the browser, the Liquid gets replaced by the data from the Connector that is connected to your Card. Check our Card Building Guide to get started with the Card Designer.
Objects are the most frequently used attributes in your Card's design as they are the ones that are directly responsible for dynamically inserting data from your JSON. Read more »
Tags are used to create business logic that tells the Card what to do. Read more »
Filters are used to modify the output of strings, numbers, variables, and objects. Read more »