The SUICA/ICOCA Cards are prepaid e-money cards that can be used for transportation and shopping (SUICA is sold by JR East and ICOCA is sold by JR West). Both cards work the same way, and can often be used interchangeably. Rather than having to purchase a train or subway ticket from a vending machine, just swipe your SUICA/ICOCA Card at the ticket gates as you enter and exit, and the fare is automatically deducted from your card. These cards can be used on JR trains, subways, buses, convenience stores, vending machines, restaurants, and many other retail outlets. They are very convenient, and it is easy to see why so many Japanese people are using them.
You can turn in the card and get a refund at the end of your tour, including a refund of the initial 500 Yen deposit and any remaining amount on the card. But a 220 Yen service fee will be subtracted from the refund. Refunds for the SUICA/ICOCA Cards can only be done at JR Stations.