Tracking is the skill used to find animals and other wandering humans on the wilderness map, especially when hunting.  It provides a passive chance to locate a trail as you travel, and you can actively search for tracks by pressing [Alt+L], or going through the [S]kills menu.

When standing over a track in the zoomed in map, you can find the direction of the tracks by using this skill. Sometimes the animal pursued will have walked in a circle, making it hard to determine the final direction. The older a track is, the more faded the track will seem.

The tracking task of the Living in the Wild course gives a boost to this skill.