As I mentioned in the Vampire Basics article, all Vampires can feed from all sources, just with varying levels of efficiency.  Here I will go more in-depth with the types of energy, their sources, and why a given Vampire may do better with one than another.


Anima

Anima is the animating force behind all living things.  Anima is Life, pure and raw.  All Vampires feed off of Anima, but Anima in it's natural state is incredibly powerful and forceful.  Trying to consume it directly would be like plugging a household toaster into an industrial power generator.  It is a very rare Vampire which feeds directly on Anima.  They are often incorrectly labeled as "Soul Vampires" as it is conceived of as them feeding directly from (or on) the soul itself.


Psi Energy

Psi-Vampires, or Vampires which feed best off of psi energy, are the most common.  Psi is Anima which has been refined for the purpose of being used as sustaining mental energy.  While it nourishes the body to some degree, it primarily follows the intention of the mind and gives energetic force behind one's actions.  Look at your hand and concentrate on it.  You will begin to feel a change of sensation within your hand; this is Psi.  By focusing your mind on your hand you also focused a lot of Psi into your hand.  While it's much less noticeable, Psi is in every action you take.  Psi is the most common energy in the human body so it only makes sense that most vampires would feed on Psi.  Without sufficient Psi a person, Vampire or not, begins to lose the associated functions.  These most commonly include clarity of thought and physical energy, and a loss of control and strength in movements.


Sexual Energy

Think of every physical act as being symbolic of the energy behind it.  Sexual energy, therefore, is the energy of Life itself.  Specifically, it is the energy of new life.  Vampires who require Sexual energy have so little Life energy within them that, energetically speaking, they age very rapidly after Awakening.  Just like old age, this puts a great deal of strain on all of the rest of their systems which means they have most of the same symptoms as a Psi-Vampire.


Natural Energy

Often conceived of as "Mana," Natural Energy is the energy which is free-floating and emanates from objects of nature.  It is created in small amounts by everything which is natural, but only a small amount is needed by a Vampire.  Those Vampires which feed on this energy the most have very little in the way of an energy deficiency, but rather have an energy dysfunction.  It is natural for our energy to be channeled out of the top of the head, move down on the outside of the body in what we think of as our Aura, and return into us in our feet and the bottom of the torso.  This cleans the energy by mixing it with the energy in the air and keeping it in motion.  These Vampires have a very inefficient system and so their energy needs to be cleaned and revitalized manually by drawing in Natural Energy.


Elemental Energy

Elemental Vampires are some of the weirdest.  They actually have enough of the energies a normal human needs.  But in addition to those, their bodies have developed a need for a charge from an element.  This happens when a person is so in tune with an element like Fire or Water that it actually becomes part of their nature and they then need to sustain it.  Since the body can't produce an energy like that they need to get them from an outside source.  It is common for Otherkin who are kin with elemental creatures such as Dragons to be minor Elemental Vampires.  However, because they are so frequently drawn to their own element they often feed without realizing it and do so often enough that they never go through withdrawals.


Emotional Energy

Emotional Energy is a highly specified form of Psi Energy.  Thoughts, like physical actions, focus large amounts of Psi.  When this energy is based in something powerful like an emotion it changes the nature of the Psi, not unlike the changes that different methods of cooking cause.  These people, for whatever reason, require this form of Psi.  Some can feed off of any emotion, which means they have a Psi deficiency but need help processing it.  By getting the energy already formed for use by the person it's like getting the energy "pre-digested."  Most people who feed off of Emotional Energy can feed off of any emotion, but have distinct favorites.  A small number of Vampires feed off of very specific emotions.  They have the same deficiency as any other Emotional Vampire, but it is in their nature to feed off of a specific emotion like how Elemental Vampires must feed off of a specific element.  Most often the need to feed off of a specific emotion is due to kinship, almost universally to a Celestial kin species.


Sanguine Energy

The energy in one's blood is the half-way point between pure Anima and Psi.  It is, in essence, the same deficiency as a Psi Vampire, but their bodies have a greater need and require the energy in a more pure form.  Psi Vampires are set up that they feed relatively frequently.  Sanguine Vampires, on the other hand, rarely have the need to feed more than once every month or two.  Both Psi and Sanguine Vampires take about the same amount of energy.  It is simply that the nature of a Psi Vampire is to take several bursts of short-lasting energy and it is the nature of a Sanguine Vampire to take a single shot of long-lasting concentrated energy.  Sanguine Energy would overload most Psi Vampires, Psi Energy alone would be burned off very quickly for a Sanguine Vampire so they would have to feed again within the day.  This more extreme need is why Sanguine Vampires typically have the most severe withdrawal symptoms.