Microsoft RPC
Microsofts implementation of the Remote Procedure Call is a modified version of the open source implementation RPC. In the beginning it allowed the implementation of more more complex costructs and evolved later to a powerful technology for creating distributed client/server programs. As well as RPC MSRPC allows to execute Subroutines on a different device. This way program can distribute some of their workload to other devices on the Network.
Connecting to MSRPC Services
Since the MSRPC services run on Ephemeral Ports the client first needs to get the Port Number of the service before he can use it. To initiate such a connection the RPC Port Mapper is used. This service is runnning on the server and is constantly listening on Port 135 to tell tell connecting devices which MSRPC services are available and on which ports they are accessible.
One popular use case is to run MSRPC over SMB you can read more about it on Microsoft Docs.