What is a Vampire?
If you ask different people, "What exactly is a vampire and what does one look like?," I'm sure that you would receive different responses.  Some would claim vampires to be the corpses of the recently dead rising from their graves to invade the homes of the living and drink of their lifeblood.  Others would say that vampires are the result of some strange, misunderstood disease, in which the afflicted persons look like average, ordinary humans while perhaps altered by symptoms of the illness.  Many would declare them to be aristocratic (or at least, appearing as such) people who were once mortal then converted at some point during their lives.  Then again, you also have those certain individuals who say that vampires don't exist at all, that they were and are the product of the wild and rampant imaginations of superstitious people centuries ago....but that's beside the point.

The characteristics of a vampire are about as varied and diverse as the people who inhabit this planet, yet they all share one thing in common.  It's the single, most basic aspect that connects them no matter their place of origin or the manner in which they are depicted:  the accepting or taking in some chosen manner the lifeforce of another in order to prolong their own existence.  An immortal, at least in some cases, parasite, if you will.
Visually, vampires are seen in more than one light.  The range of physical appearances can be rather wide.  Some are seemingly the epitome of an Adonis or Aphrodite, beautiful in every way, while others are hideous and horrific visions of rotting corpses.  Some look like your run-of-the-mill human being while others bear a strange countenance, where you know that something's wrong with them or off....yet you don't entirely know what.

Also, what these creatures need and desire in order to sustain themselves can be as distinct as their outer guises.  A great deal of people believe that all vampires need blood when, in actuality, this isn't the case.  Depending on the region and culture, some vampires seek to obtain the energy and vitality of other beings.  Some prefer the actual flesh.  Some even thrive on their victims' pain, suffering, and fear.
Another thing is that though the majority of vampires are primarily nocturnal, not all of them will be incinerated by the light of the sun.  Some do move about and feed during the daylight hours, but more often than not prefer the comfort and darkness of night, when they are more alert, relaxed, and feel they're in a far more familiar atmosphere.

Please keep in mind that this is just the tip of the iceberg.  Information on vampires flows on like an endless stream of crimson vitae.  They certainly aren't one-dimensional monsters.  Not all are even wicked or malevolent as many people view them to be.  Just as with other beings in existence, good as well as evil are amongst them.  They can be just as complex and three-dimensional as humans.  So don't be fooled and assume that the person living next door to you is just another fellow human.  He or she could actually be the person of your dreams....or nightmares.