Pass-by-reference referes to one of the two major ways arguments are passed to methods (the other is pass-by-copy). In a pass-by-reference scheme, arguments remain in their original memory localtion and a pointer to them is passed to the callee method. This means that if the callee changes the value of an argument, the value of the caller's variable changes as well. This is particularly important to Babel RMI, where object can be passed either by copy or reference.