The term "502 Bad Gateway" refers to an HTTP status code that indicates that a server acting as a gateway or proxy received an invalid response from an upstream server. This often means that the server is unable to communicate with another server, leading to an error when trying to process a request. Users typically encounter this error when accessing a website or web service, and it suggests an issue with the server rather than their own internet connection.
The term "502" comes from the HTTP status codes defined in the Internet Engineering Task Force (IETF) standards. "Bad Gateway" describes the nature of the error, where "bad" indicates a failure and "gateway" refers to a server that acts as a middleman between different servers in a network.