Skills and talents are quite confusing. Trade Skills are more like crafting, or gathering. They are separated into common and professional (my word not blizzards). Common skills everyone can learn, Professional ones are the ones like Tailoring, Blacksmithing, etc. Included with the Gathering ones, Harvesting, Skinning, and Mining. You get to learn a maximum of two from of all the professional / gathering skills. In Stress test they were controlled by skillpoints. According to blizzard you not purchase the skills and recipes with currency or find recipes in quests, droops. In the stress test you could unlearn your trade skills, now I am not so sure. I think you are stuck with the one you choose, or at least no currency refund if you do unlearn. As I am not a tester any longer I do not know for sure.
Passive skills are learned through a purchase, then usage. Each class had some of these right from the start though. These are the skills like, unarmed melee, dagger, language, so on and so forth. They are passive, but improve the status of your character. I never got to a level to purchase a new passive trait, but they do exist, and more should be implemented. These can not be unlearned.
Combat skills are not as well known to me, think of them as spells for melee people. You train for these at your local melee combat trainer, or ranged if you use bow. That’s about all I know. As I haven’t followed up on these as much as magic issues. I will be a warlock, not a warrior, at least not for a while.
I believe the reason for the change in skill points was the fact that skillpoints were used for both craft and melee skills, giving a big disadvantage to melee crafters.
The last thing is Traits. These are the abilities like your skilltree in D2. Most of them are passive, but some are active. They are a big part of your character customization. So far each job has 3 different trees related to that job, and about enough trait points to max one max. As this is a system implemented after the stress test I have no experience with these and leave it at that.
This is information I have gathered over my own research and drawn from memory. The different systems are confusing and with all the changes made in the last few months hard to track down. Hope this helps you all, and good luck in the game.
Please forgive me, and correct me, if I made a mistake.
Any further questions or checking use this site: http://www.worldofwarcraft.com/
The FAQ on the blizzard site is rarely updated, therefore not always correct.