A "callback URL" is the web address an API needs to send information for use by a different web site. You will need to have a system that can accept http requests from our server in order to use the callback_url and status_url. This has been tested with JAVA and .Net applications.
This category of APIs include details for methods that are applicable at a tenant level such as carrier lookup, reading organization tree, Read Verification Type, MMS and Reverse Lookup.