The virals are vampires in the sense that they drink blood, can infect others, have superior strength, are very fast and can only be killed by a blow to the heart, not for supernatural reasons but because their bone density increases rapidly, aside from an area in their chests which is vulnerable. They can also be blown to pieces, set on fire, beheaded etc. They are long-lived, but not immortal. At 92 years after the initial infection, it appears that some are dying, although it's unclear if this is from lack of food or simple age.
The normal virals have an instinctive recognition of people from their former lives, but are otherwise unintelligent. They are less sophisticated and smart than the vampires in I Am Legend, and for the most part are treated as 'fast zombies' from the likes of 28 Days Later.
The exception are the Twelve, the first twelve vampires infected with the chemical version of the virus. The Twelve are intelligent and capable of limited reason and negotiation, but are still unrelentingly hostile. Each one of the Twelve has a sort-of telepathic communication with the other virals he infected, or infected by those he infected and so on. Effectively, all of the vampires are part of a lineage of infection extending back to the Twelve. The Twelve also have the ability to project into the minds of normal humans, disorienting them and even driving them crazy, but they must be close by to make this work. Killing one of the Twelve severs the connection between the members of the lineage and makes them vulnerable to certain influences and counter-weapons, which really would be a massive spoiler.