FrontendBackendGeneralTable-stakes
JSON
Also written as JavaScript Object Notation
The standard text format software uses to send data back and forth, especially between web apps and APIs. It's readable by both people and machines.
Think of it like
The standard shipping label format everyone agreed on, so any courier can read any parcel.
Junior or senior?
Universal, so it says nothing on its own. Never lead a screen with it.
Ask them
“Tell me about a time data passed between two systems as JSON broke something, such as a missing field or a wrong type. How did you find it and fix it?”