Gathering consists of the following professions: Fishing, Harvesting, Logging, Mining and Tracking & Skinning.
The gathering skills makes use of tools to gather raw resources from the land and water. You will need the right tool for the right job. For example if you want to fish you will need a fishing pole. If you want to log trees you will need a logging axe.
The skinning knife is used for the Tracking & Skinning skill where you harvest the fur from dead animals. As you level up the skill you are able to also track these beasts on your compass.