Paperless geocaching refers to the use of a Palm or Pocket PC in the field to access the information from the cache pages instead of using pages printed from the web site.
To get the information into your Palm or Pocket PC, you need to download the .gpx files which have not only the coordinates for the cache, but the information about the cache, including the description and the hint.
If you take up Paperless caching, make sure you keep the information in your Palm or Pocket PC database updated. There is nothing quite so frustrating as looking fruitlessly for a cache that is in both your GPSr and your Palm and then finding out it went missing a few weeks earlier.
Cachemate is a great program for Palm-based handhelds designed specifically for paperless geocaching