This exception is considered the top-level or "catch-all" for problems related to HTTP requests made towards App Services. This covers both HTTP transport problems, problems passing JSON or the server considering the request invalid, for whatever reason.
Generally, reacting to this exception will be hard, except to log the error for further analysis. But in many cases a more specific subtype will be thrown, which will be easier to react to. See the subclasses of this exception for more information about these.