question about RPC

This may be a bit off topic but I begin with understanding of php and doing synchronous and async queries generated by javascript on the client side. Recently I resurrected a home built server and installed FreeBSD. Since I have been doing probably as much javascript as php, I have been interested in exploring node.js. My question is academic How is a simple query from a client like Firefox to an http server using php to process the request different from RPC? (I have been looking at Wikipedia article on RPC: http://en.wikipedia.org/wiki/Remote_procedure_call) I have written call back functions that are invoke from a window opened in javascript that call functions in the opening window. And as well, calling a server side script generally involves calling functions and methods and sending a result back to the client. For instance, there may be a form that is used to compose and execute a query of the server's data base server (MySQL, Postgres, etc) and the result is assembled and sent back to the client for display. How is this different from formal RPC? Now there is Apache Thrift with bindings to node.js (and other languages), which seems to imply that php can hand off requests to a node.js server, that might in turn satisfy a client request. (node.js is server side javascript) Right now I wouldn't do anything outside of localhost with node.js because it looks like asking for a whole lot of trouble if used over public network. Are there any academic thoughts on this? Thanks for time attention and consideration JK