Orbjson is a JSON-RPC object request broker for JavaScript/Ruby RPC interaction.
Communication between client and server is done using JSON, the JavaScript object notation
Orbjson takes JSON-RPC requests, locates the correpsonding server-side object, deserializes the requrst, and invokes the method call.
Orbjson then takes the results of this invocations and sends it back to the client as a JSON-RPC response.
JSON-RPC is a variation on XML-RPC; it is a lightweight remote-method invocation protocal that uses a plain-text wire format. That format is JSON, which defines how to express native JavaScript objects as text.