Not a bad explanation, vormel. I'll certainly grant you that one. Though, in my mind, there are a few things missing, there.
To put it into the perspective of someone who has been living as a vampire long enough to know--
"Vampire spirit", yes, is essentially no more than another term used to describe an ethereal entity that feeds on the energy of the living. But that is only one of the many terms used to describe the exact same thing. In fact (speaking as former reverend/"man of the cloth", as well), very rarely are any spirits referred to as "vampires spirits". Instead, the most commonly used term is simply a "demon" or something similar. I would personally describe it as no more than a "hostile entity". Plain and simple.
Furthermore, a real vampire is simply a person who requires a sustenance that they can't gain from "normal human food or beverage". Again, from the perspective of someone who has been living this way for long enough--
As a vampire, myself, I require fresh blood, just to maintain my health (both physical and psychological), which is "both a blessing and a curse", due to the fact that I try to refrain from "feeding" from anyone unwilling. But the vampire, by nature, is a (mostly nocturnal) predator in many ways. Now, there are those who are what you might call "social vampires", which is nothing more than a person who "feeds on the energy (or energies) of others, via essentially wreaking havoc in their lives. But I would by no means refer to these people as "real vampires". A "real vampire" is simply one who naturally possesses the necessity to consume energy from someone or something else, and cannot gain that sustenance from any "normal" means.
Normal human beings can eat, drink, whatever have you, and go out in the sun, for their Vitamin D3, to gain their energy and assist their health, etcetera. vampires, on the other hand, do not really have that option, as they do tend to be very sensitive to light, as (again, mostly) nocturnal predators by nature. Obviously, this doesn't mean they turn into ash or whatever, from being out in the sun. But the natural sensitivity (to light, in general) does tend to make the vampire very adverse to the light of the sun.
In some cases (my own, for example), too much sunlight will often make a Real vampire quite agitated, induce much more severe migraines than most would already experience, cause a sometimes extreme sunburn, etcetera.
But, at the same time, if the 'Real' vampire is properly sustained (i.e., nourished), then the capacity is thus enhanced to the natural level, being quite (or by far) beyond what the average human being is capable of handling. Strength, speed, reflex action, and more, become completely inhuman, while also, at times (again, myself as an example) completely reversing the body's typical aging process.
So, in short, a "vampire spirit" is basically (as vormel states) nothing more than another term used to describe a hostile entity that feeds on the energy (or energies) of the living. A 'Real' vampire simply requires a more particular manner of sustenance that cannot be attained via "normal" means. In some cases, this means by consuming fresh blood. For others, it may be the psychic energy of another living being. Or, in the extremely rare case; there is something called "Psionic", which most people essentially lump in with being something no different from a "Grimm Reaper", as they literally feed from the energy generated by the one thing that cannot be scientifically measured with ease: spiritual or metaphysical energy (i.e., the soul or spirit, as most would call it).
Mind you, either vormel or my own descriptions, here, are barely even scratching the surface of it all. There is really no way to properly describe it for you, without having to go into highly vivid detail.
