JSON is a text format for arranging information so different programs can exchange it. It is like a neatly labeled form: each value sits beside a name that explains what it means.
A service might send a person's name and account number as organized text. An app can read that information and show it on a screen.
People usually do not need to read JSON by hand, but it is useful when programs communicate. The names and values must follow the format's simple punctuation rules so the other program can understand them.