Serpentine belt is the one you can see when you look in the
engine bay. It is rtunning the AC, alternator, etc. These
used to be called fan belts. They are replaced at 60K intervals.

The timing belt is under a black cover on same side of the engine
as the accessory belt. They are changed at 70K intervals. This
is connected to the two cam shafts at the top then to the crankshaft
on the bottom. Water pump is also driven by this belt. There is also
a tensioner and idler wheel down in there. Note that later build 98s
have a newer timing belt design. Search this site for
"mechanical tensioner 1998" (bleow to the right) for details (you
should be able to track down the serial number at which the new
design was introduced).