Skillbook
The skillbook for your certain type of class (warrior, priest, mage, hunter) is essential for making the most out of the skills provided so that you can enjoy the game a lot more. This can be found in the Status Window located bottom left of the screen next to the "Equip" tab with the little brown book on it.
General Information
When you open this tab, it shows you a "General" tab which holds your default skills like Auto-Attack, Alchemy, Cooking, and Analyse. It also includes the controls for your pets like Call Pet, Revive Pet, Pet: 'Attack', Pet: 'Follow Me', and Pet: 'Stay Here'.
The next tab over holds all of your skills that are unique for your class. Up in the right hand corner, there is a counter for your total number of skill points that are available. As you level up, this counter will go up by one. You can spend these points on skills of your class to increase power and advantages.
Some skills may be unavailable to you if you are not leveled enough or you need another skill first before you can obtain that specific one.
Class-Related Links
To find out more about your class and how your skills work, have a look at the following pages: