JSON is also a type of variable. It is used to store and manage a series of variables including normal varialbe and JSON variable.
For example, this is a JSON storing a customer's detail:
Check this tutorial video about how to write JSON variable.
The "JSON Operation" is sitting in the "Basic Actions" list of the Action step.
TIP - Various examples have been already embedded in the operation. Select an operation and use the "Examples" button to explore it!
For example, how to insert an item to a JSON variable: