Hike descriptions are intended to act as a trail guide. They describe what turns to make to follow the hike route, with distances (which can be measured with GPS or a pedometer) and also describe natural and artificial features of interest along the trail, such as unusual trees, other plants, ruins, streams, rocks, and so forth.
KML (Keyhole Markup Language) is an XML standard developed by Keyhole, Inc., later acquired by Google, for exchanging geographic information. These files can be viewed as an overlay either in Google Earth or Google Maps.
Google Earth is a standalone application which must be installed on your computer before you can use it. Once it is installed, simply download the KML file to your computer and use the "File" menu in Google Earth to browse to and open it. You will now be able to view the locations of the trailhead, trail, and any points of interest along the way projected onto aerial photographs, which can be "flown over" in 3-D.
These files can also be used online in Google Maps, which does not require any software installation. Use your context menu (right-click) to copy the link to the KML file to the clipboard. Then, browse to maps.google.com and paste that link into the search box, then search. The KML file will now be displayed as an overlay on Google Maps in your web browser.
The KML files will show the route of the hike, trailheads, and nearby points of interest, but will not necessarily show all connecting trails.
The GPS tracks are stored in GPX format, which is an XML standard read by almost all GPS devices. Download them to your computer and use the software supplied by your GPS manufacturer to upload them into your GPS. The trail for each hike is stored as one or more tracks; other trails are not necessarily shown, to save space.