An "HTTP 500" error, also known as a "500 Internal Server Error," indicates that something has gone wrong on the server hosting a website. This error is a generic message, meaning the server encountered an unexpected condition that prevented it from fulfilling the request made by the client, such as a web browser. When users see an HTTP 500 error, it typically means that the server is unable to process the request due to issues like misconfigurations, software bugs, or server overload. It does not provide specific details about the problem, making it necessary for web developers or server administrators to investigate further to resolve the issue.