The term "4xx errors" refers to a category of HTTP status codes that indicate a problem with the client's request. These errors suggest that the server could not process the request due to issues like a missing page or unauthorized access. Common examples include 404 Not Found, which means the requested resource is unavailable, and 403 Forbidden, indicating that access is denied. These errors help users and developers understand what went wrong when trying to access a website or resource. By providing specific codes, such as 400 Bad Request for malformed requests, they guide users in troubleshooting issues related to their requests.