type "df", or "df -k" for a slightly more understandable output.

each of the paths listed there are a mounted partition of a disk. if you're on a sun, the disk names will be the things that look like c0t0d0s0.

The c is for controller number
t for target number
d for disk number
s for slice (partition) number

A disk with 2 partitions might have two entries like this

c0t0d0s0 /usr -- rest info
d0t0d0s1 /usr/local -- rest of info