Reminiscent of Ultima Online or Asheron's Call, Shards Online uses a "what you do is how you progress" type system with skill lines from basic combat to animal taming, harvesting, magic, and the full run of crafting skills as well. As you can see in this news article that has been recently released by Citadel Studios, Shards Online has very diversified and interesting skill system. You have 5 type of different skills that grant you access to many abilities. For example, in the magic line, Manifestation (a skill) allows Fireball, Lightning, Heal, Resurrect, Teleport and others abilities to be used.
This is just a preview of the system, however, it contains a lot of skills and abilities. So, if you want to dive deep in the Skill System of Shards Online, visit this news article. In the coming days, the developer plans to release a more detailed explanation concerning each skill, the way to use them as well as player and developer suggested builds.