The PASMO IC card is a pre-pay card you can use in Tokyo and Kyoto
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 several pre-pay cards
including PASMO. Recently all these cards have become pretty interchangable. For this trip you
will get a PASMO card with ¥2,500 already on it.
There is a home page for PASMO here. Wikipedia
has a pretty comprehensive article on PASMO.
Another helpful site.
Note that when you are done, please return your PASMO card to the chaperones so
we can use them on later trips.