Class Skills in Elder Scrolls Online are what distinguish players apart. Each player is able to use any of the Weapon Skill Lines or Guild Skill Lines etc, but these are the only Skills that are not available to everyone. Class Skills afford drastically different play styles. And, since the player is free to use any weapon he/she wishes, the combinations are limitless.
Each class has three different skill lines associated with it, which are immediately available to your character and are specific to your class. Each skill line consists of one Ultimate skill, several passive skills, and active skills. Passive Skills provide a bonus all the time. Some require certain items to be equipped or Active Skills to be slotted. Active skills have 4 ranks and 2 morphs, using your Active Skills will increase your overall level in the skill line, making new skills become available as you progress.