Hypertext transfer protocol (HTTP) is an application-level protocol that is used to transfer data on the World Wide Web. It works on the request-response model i.e. a client, typically a web browser, makes a request to a server, which is hosting the web application, responds to the client with relevant details.
The first line of the response contains a status code and description. HTTP Error 500 Internal server error is one such error or status message that the server sends when it is unable to retrieve the page or perform an activity that the browser has requested.