[ Disclaimer, --- , ]
This skill enables you to locate targets in the vicinity. The higher the skill, the farther away you can detect your prey. While bards and druids share this ability, the ranger class excels in this skill and is able not only to track by spawn order but by mob level as well, via the "track sort" drop-down box.
Note: Maximum number of tracked mobs reduced to 20 on 7/14/2013 patch? 
Due to a bug, it appears that your max skill is 20, but your actual skill will level up beyond that.
Bard tracking is less distance than you can see with max clip pane
Performed testing on tracking distance in WK. Tracking Skill Formula: Distance = (Tracking Skill) x 12.
Example: Distance tracked = 75 skill x 12 = 900 range by \location
Bard formula: Distance = (Tracking Skill) x 7
Druid formula: Distance = (Tracking Skill) x 10