Capcom has thus far mentioned two primary enemy types for Resident Evil 6: zombies and J'avo.
Zombies, which are making their return to numbered RE games with RE6, have evolved some. They'll be able to run, jump, and make use of weapons.
Zombies are nothing compared to the fierce J'avo, though. J'avo, which make their debut with RE6, have intelligence. They understand language and work in groups. They can also wield advanced weapons. If injured, they'll heal themselves and may even change into different forms during regeneration.
The J'avo and zombies all emerge from the same virus. RE6 debuts the new C-Virus. Those who are infected with the C-Virus will temporarily change into a cocoon-like state "pupal" state Inside the cocoon, they'll undergo a dramatic transformation and eventually emerge in their final form.