Vampirism

Vampirism is a concept of energy siphoning off of another. People who are referred to as "Real Vampires" are those who cannot produce their own energy, so are forced to take it from another. The different "types" of vampires are only really which type of feeding is preferable to the individual. It doesn't mean a different species or that you're locked into that kind of feeding. The types are just named for where the energy is pulled from. Ethically, the target is a willing donor, but it's not required. Close proximity makes the process easier, but with practice long distance feeding is possible as long as you can establish the connection with the intended target.  
Anyone can do and probably has done the feeding techniques. The thing that makes the person a vampire is the need to. These techniques can be done individually or combined. There are ways of performing astral sex with a being from another plane then feeding off of it, which is both sexual and astral.
The feeding techniques are often used by necromancers to regain energy and health lost from working so closely with the dead at the expense of those around him or her.
Just a few of the techniques are:
Sanguine is possibly the most famous from movies, that is taking from blood. It is the most dangerous for obvious reasons. The energy gain isn't from the blood itself, but from the life force within the blood.
Psychic is another popularly known one. This one is where the person will feed off of another person's aura. There is the possibility of picking up whatever bad energy the donor has. This is newly termed pranic.
Empathic is where the person feeds off of emotion. This can be beneficial to the donor due to the removal of energies that could be causing blockage or harm.
Sexual used to be called pranic years ago, but now it's just termed sexual. This is feeding off of the excess energy produced during the act of sex. Makes for an intense experience for both parties, especially when combined with another technique or two.
Elemental is probably the most common among humans. It is common among a chunk of religions and spiritual views to gain energy off of the elements.
Astral is feeding off of astral beings during your own astral projection.
Dreamscape is when you dream walk into another's dreams and feed off of them.
Soul is the most intimate form of feeding. It's when you drain a person's soul. You can gain the strength, abilities and memories off of the donor during this type of feeding.
Magickal is the ability to use magick and feed off of the energy produced during the ritual.