Error messages are notifications that appear when a computer program or application encounters a problem. They inform users that something has gone wrong, often providing a brief description of the issue. These messages can help users understand what needs to be fixed, whether it's a simple typo in a form or a more complex issue like a software bug. Error messages can vary in complexity, from straightforward alerts like "404 Not Found" to more detailed explanations that include error codes. Understanding these messages is essential for troubleshooting and resolving issues effectively, allowing users to take appropriate actions to correct the problem.