I am learning about REST services and from what I understood until now the only difference is the language of the file that is outputted by the script that runs as a backend.
Can a regular web server that outputs a HTML file that contains the number of users of a website be considered a REST web service? After all it can be called by a program using a GET request and in the response body there is the number of students inside some tag that can be programatically read by an application after parsing the HTML file like it would parse a JSON of XML in case of more traditional REST service.
There are also web pages where it shows for example details of a book and the book id is sent through the GET request URL. That response may again be parsed by an application that called that URL with the GET verb and than the program can find out information about the book if it knows what is the structure of the HTML file. That again may be seen as a REST web service in my knowledge.
Am I wrong in the way I understood REST services until now?