An "HTTP 502" error, also known as a "Bad Gateway" error, occurs when a server acting as a gateway or proxy receives an invalid response from an upstream server. This means that the server you are trying to access is not able to communicate properly with another server that it relies on to fulfill your request. This error can happen for various reasons, such as server overload, network issues, or misconfigurations. When you encounter an HTTP 502 error, it typically indicates a problem with the server infrastructure rather than your device or internet connection.