These are findings by me with my little experience with Solaris 10. Please correct me if wrong..
In x86 systems with ide hard disk:

c= controller
d=disk
s=slice

1.Here controller c0 means the primary ide controller ide0.
controller c1 means the secondary ide controller ide1.
controller c2 means the external drives such as usb drive.
3.c0d0 = disk connected as primary master.
c0d1=disk connected as primary slave.
c1d0= disk connected as secondary slave.
c1 d1= disk connected as secondary slave.
4.s means the slices (partitions) we create in d0, d1, d2, or d3.

For eg. the primary master hard disk's 5 th slice will be:
c0d0s5
the secondary slave hard disk's 6th slice will be:
c1d1s6

Usually, in x86, the target number is not specified. I dont see an entry in /dev/dsk directory...( is it not?) . Not sure about this. Please clarify.

5.If you connect an external usb drive, it will be treated as:

c2t0d0p0. Am i correct?