As an analogy, RPC works as a function call. Like a function call, when an RPC is made, the calling arguments are passed to the remote machine and the caller waits for a response to be returned from the remote machine.
The below figure shows the flow of activity that takes place during an RPC call between two networked machines:
The client machine makes a procedure call that sends a request which included program number, version number, procedure number & etc to the server and waits. The thread is blocked from processing until either a reply is received, or it times out. When the request arrives, the remote machine calls a dispatch routine that performs the requested service, and sends the reply back to the client procedure. After the RPC call is completed, the client program continues.
A client system connected to a database server may execute an RPC to process data on the server. For example, a computer without a hard drive may use an RPC to access data from a network file system (NFS). When printing to a network printer, a computer might use an RPC to tell the printer what documents to print.