RMI stands for Remote Method Invocation and is a Network Layer to let a client application to invoke methods of objects located on a remote server.

The word "RMI" is not specific to the Java language: RMI concept is not recent and not chained with Java, it knows lot of implementation in all other languages. RMI can be considered the object orientation of RPC (Remote Procedure Call).

Speking in a Java context we should specify Java RMI as a protocol that let a remote object happens to live
in the local machine.

RMI was considered tedious and error-prone to implement, Java made it easier using a simple model based on a Remote interface a class implementing the Remote interface and an automated stub/skeleton compiler.