The SUICA IC card is a pre-pay card you can use in Japanese metropolitan areas
for most buses, trains, and subways as well as in some stores. The
"IC" stands for "Integrated Circuit" or "Integrated Chip" as the
card contains an embedded chip that remembers your balance.
This page describes two pre-pay cards:
PASMO and SUICA. In most metropolitan areas these cards are interchangeable. For this trip you
will get a SUICA card with ¥2,500 already on it.
There is a home page for SUICA here. Wikipedia
has a pretty comprehensive article on SUICA.
Note that when you are done, you can claim any unused balance on your card. Frankly,
it's quite a hassle to do so, and we don't expect the remaining balance to be very
much. My thinking is just keep it as a souvenir or give it to someone local for their use.
Or, you save it for your next trip to Japan: just top it off at a train station or
selected stores and you're good to go.