The answer to this question is similar to the relationship between squares and rectangle. All squares are rectangles, but not all rectangles are squares.
All REST APIs are APIs, but not all APIs are REST APIs.
REST (REpresentational State Transfer) API (Application Program Interface) is an architectural style on how to structure and build an API. REST APIs are build upon:
- HTTP protocol
- JSON for a data format
REST APIs are built for simplicity and make it really easy for developers to use APIs. What makes then so simple to use is the fact that it is build upon the four following HTTP requests:
Another term you might hear when talking about APIs is SOAP (Simple Object Access Protocol). SOAP is more complex and has less freedom because it defines more standards like security and how messages are sent. There are pros and cons to both, but REST APIs is the more preferred style of API.
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