1) A vampire seems to be a creature (human, human-looking, or otherwise) which feeds off energy (from emotions, or some life-force) be it psychicly, or through the blood of a victim.
2) As far as I can tell, the vampire lives the same life as you or I. May be enrolled in school or go to a job, and is not inherently a "night person", though it is generally accepted that they are at least a little light sensitive.
3) As I've said, it does not always get sustainence from blood. But in the case that it does, I honestly have no clue. If someone can tell me, I'd be happy to listen to theories.
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