RPC or Remote Procedure Call and gRPC

RPC Definition:

Remote Procedure Call (RPC) is a protocol that one program can use to request a service from a program located in another computer on a network without having to understand the network's details.

A procedure call is also sometimes known as a function call or a subroutine call.

Tutorialspoint:

https://www.tutorialspoint.com/xml-rpc/xml_rpc_intro.htm