RS-485 is actually a physical layer specification which allows multiple nodes to be connected to a differential 2-wire bus. Unlike RS-232 which can be full duplex (transmit and receive at the same time), RS-485 exchanges must be half duplex. This means there must be rules about who can talk and when. The most straight forward way to start experimenting with this is to connect a UART to a transceiver (LTC1485 and others) and have a go at it. Of course you'll need another node to communicate with, but that is a minor inconvenience.