RR works on the first come first served basis but, the difference is that it has a "quantum". The quantum is a maximum time period that the processor gives to the process at a time. If the process is longer than the quantum it is put at the back of the queue and when it gets to the front of the queue once again it is completed further. It does this until it is finished. Numerous processes are in the queue and all wait for their turn so, remembering the processes and their order is important. I also assume that if a new process appears at the same time as a queued process it would be started first, not too sure on that but it shouldn't matter too much.
Here is a real life example:
person serving = processor, number of items = burst time, number of items that can be bought at one time = quantum, queue = process queue, people being served = processes
There is a food queue at the local fast food shop; it's rush hour and everyone wants something different (the different processes). There is only one person serving the queue and each person being served can only buy one item at a time (quantum = 1). The first person gets to the front of the queue and buys a hamburger but is still hungry and joins the back of the queue. The next person wants a hotdog and is done and so leaves the queue. the following person wants an egg sandwich but is still hungry and joins the back of the queue. The person who wants another hamburger is served again but is still hungry so goes to the back of the queue. This continues until the queue is empty or the shop closes.
