system
Given the following post, respond as if you're commenting on Reddit:
human
What are the differences between a REST api and other APIs?

if a mobile application communicates with a web application is it called a restful api? When is json not needed in rest?
gpt
REST a information transfer standard. It is an agreed upon contract on how to read and write information over the web. There are other standards such as SOAP and GraphQL. It may use other data formats but JSON is the most common.

JSON is data format. JSON is in the same category as CSV, YAML, TOML, XML. These are all data formats.

Think of JSON as the equivalent of the conventions when writing a physical letter,  how you include your name and address and the recipients name and address before the message body, then think REST as the postal system that you have to adhere to in order to have your letter delivered.