Rest API how to use it?

Question

RESTful API

There is a site that interacts with the MySQL database, takes certain data, filters it, and forms an html page out of it. The task was to develop a mobile application that will perform all the same functions as the site. To simplify development, it was decided to create a REST API that will accept http requests and return data in json format.
As I understand it, the rest api should be used both on the site and in the application, is it necessary to redo the site logic in such a way that it uses the rest api so that everything is in one place. Those. would it be acceptable if, when opening a page on the site, a subrequest to its api would be executed to obtain certain data?
If you make http scripts that will process requests and return a response in json format, can it already be called a REST API?

Answer 1

What is REST API in brief . Good systems work this way, only with intermediate caching.
REST for the most part simply does not store the state of the client and data, so what you are asking is most likely yes, it can be called