Simply put, a vampire that has lasted amongst the undead longer than two hundred years' time. Why is this considered ancient? Well, because with the demons that hate vampires, and would go after the powerful ones, the Watcher's Council, and the Slayers running around, their life expectancy isn't too high. This isn't including the fact that other vampires could kill them for their power, since most Ancient Vampires have power and have established themselves.
Fledgling Vampire
A vampire that hasn't been amongst the undead for more than twenty-five years. These vampires more than likely travel with their sires, learning all the ropes from them. These vampires are not as strong or lethal as their older counterparts, and especially not as powerful as their ancient counterparts. These vampires have little in the ways of influence amongst their kin.
Vampire
The 'generic' vampire. These members of the undead have been un-alive for longer than twenty five years and less than two hundred years. The older a vampire is within this ranking, the more likely they are to have power, influence and childer loyal to them. The younger they are, the more likely they travel with their sire still.
Potential Slayer [1/2]
Females that could become the Slayer the instant the current Slayer dies. These girls don't have all of the physical conditioning THE Slayer has, but they still have some benefits. They are often trained by Watchers for combat and in the Occult, making them knowledgeable of the demon world and making them talented - amongst humans - in a fight.
Slayer [1/1]
THE Slayer, THE one girl in all of the world. She who is destined to fight the vampires, the demons and the forces of darkness. Most unfortunately, this job, despite the perks of super strength, agility and constitution, has a life expectancy of twenty-five or younger.
Demon
Creatures from the hell-dimension. However, these beings have quite a lot of human in them. This is because all of the True Demons were imprisoned in the other dimensions, leaving the weaker cousins behind. Since these beasts are few and far between, they've often had to breed with humans over the centuries. This makes current demons humanoid and often prone to human weaknesses, namely emotions.
True Demon [0/2]
What separates a true demon and a normal demon - human emotions and human relations. True demons do NOT have any human emotions of any sort and simply desire to destroy all of humanity as a whole. They also lack the human relations that their weaker counterparts do, meaning that they are rarely humanoid looking. Normally these powerful demons CAN assume the form of a mortal, but they usually stay in their true forms, which can be just about anything. These demons often have VAST power, which is why there are so few of them; most, if not all were/are imprisoned in a hell dimension.
Mortal
Normal, average-Joe human. These "mortals" come in all shapes and sizes and a variety of colors. Humans are not very strong, or fast or resistant, nevertheless, they are intelligent and adaptable beings. Some even know about the existence of the supernatural and are able to deal with it without going insane.
Shapeshifter [0/3]
A VERY rare type of human. These humans are capable of shape-changing to almost anything. There are only two different types of shapechangers, one rarer than the other. There is a shape-changer capable of shifting any of their features, or their entire body, into the form of another human. This is the more common type. Then there are shape-changers able to shift themselves into ONE animal form at will. But, they can also shift themselves to any form in-between that animal and their human form, meaning half-animal, mostly animal or mostly human forms. These are the rarest of the two.
Watcher [0/1]
Mortals of any gender destined to train the Slayer for her duties. They must train her in the ways of physical combat as well as her mind for the occult knowledge.
Werewolf
Humans cursed with lycanthropy. During the lunar cycle (the day before the full mood, the full moon, and the day after the full moon), they go into a wolf-like form. While in this form, they seek out sexual energy and go to feast where it is strongest. This means they will eat, maim and kill any humans within this vicinity.
Witch
A mortal with magical knowledge and capabilities. Regardless of what they say, a witch can be either gender since the term "warlock" is often used for an outsider of a coven or of a magical community. Witches can range in power, whether it be making simple charms for luck or combusting an entire city block in flame.