Level

A player's level in an individual skill represents the amount of Experience earned scaled by the use of an equation. To simplify it, the level tells you what you can do and what you can't. In order to do a variety of actions you need to meet the requirements. Most of the time, the requirement will be a specific level. For an example you need at least level 15 to mine Iron Ore and at least level 3 to use a Stone Pickaxe.

Here is how your Levels are graphically displayed in-game: In each slot you have a unique skill. (Only pay attention to one of the skill tabs, they are just 2 different textures) The Textures seen below are the icons for each and every skill.