So, we know that The War Z is a MMORPG. As with this genre, you expect some form of points and leveling system. Well, you're in luck because that's exactly what this post will explain to you!
By exploring the world, killing zombies, murdering other players and "doing other things in the game", you will gain experience points. You can then spend these experience points to either unlock more characters or more importantly, train up your current characters.
When I usually think of training up a character, I think of increasing their health, their strength and how hard they hit but with The War Z, it's slightly different. To keep with the idea of a realistic zombie apocolypse, you can only increase abilities that you could increase in realise life. Therefore you can increase your sprint time, how much you can carry in your backpack or how fast you can reload your gun but you can't increase your health or the power of your gun. This means that you won't have any super humans running around murdering everybody.
To me, this sounds very appealing. I love the idea that I have to train rather than level my character. I have to teach him things rather than him magically getting them.
The developers have also released a preliminary design of the Skill Tree. Each colour reptresents a different area of expertise.