As Klaus stated, RS232 is a voltage level definition for serial communications, it has nothing to do with UARTs although in most cases one is 'behind' the RS232 interface. A UART is a serial to parallel and parallel to serial converter with extra framing circuits and error detection circuits, it can be used for any kind of serial data.
A protocol defines a method of passing data between two devices, it refers to almost every serial interface whether it is a modem, programmer, Ethernet, GPS etc. It just describes the format of the data bits and how the receiving end should respond to them.
You can use a single RS232 port for many purposes, it depends on the software driving and listening to the port. There is no such thing as UART protocol though.
Brian.