From the post:
Rage consumes you in battle. You delight in carving through your enemies using powerful weapons and wreaking havoc without needing complicated techniques or rigid training, and you rely on your astonishing durability to get you through a fight. You associate your rage with a traditional symbol of affinity known as a totem, which might take the form of an animal, a spirit, or even a part of yourself. To many barbarians, brute force is a hammer and every problem looks like a nail; to others, the dark emotions within them are something to hold back and release only when it matters most.
When it came to barbarians in the playtest, we wanted to take the most popular parts of the original barbarian and the unchained barbarian and brew them together with a few special ingredients to make the class even more flexible to fit even more roleplaying and mechanical concepts. Let's take a look!