"Wands are only as powerful as the wizards who use them...." -Hermione Granger

Now that you have acquired your wand, what resides in its core? Each wand has one of the many cores used to make a wand, the most popular being Dragon Heartstring, Unicorn Tail Hair, and Phoenix Feather. Let's take a look at the difference between cores:

Unicorn Tail Hair: produce the most consistent magic, least likely to turn to the dark arts, they do not make powerful wands, and are generally the most faithful wand to their original owner. Known owners include: Ronald Weasley, Cedric Diggory, and Draco Malfoy.

Dragon Heartstring: produce the most powerful, flamboyant spells. Tend to learn magic quicker than other wands, and can be the easiest to turn to the dark arts, but not on its own. These wands generally are the most temperamental. Known owners include: Hermione Granger, Bellatrix Lestrange, and Mr. Garrick Ollivander himself.

Phoenix Feather: very rare to come across, generally produce the greatest range of magic. These wands are hard to tame, and their allegiance is not easily won. They show the most initiative. Known owners include: Harry Potter, and He-Who-Must-Not-Be-Named.

Thestral Tail Hair: rarest to come across, and not easily seen, as in order to achieve the hair you need to be able to see the Thestral (aka witness death). Known owner: The Elder Wand. 

Veela Hair: said to be incredibly temperamental. Known owner: Fleur Delacour.

The core type is known to influence the "personality" of the wand produced with it. Another interesting fact is that if two wands share the same core from the same source-much like Harry Potter and Lord Voldemort-the wands are said to be brothers. Ollivander is best known for his use of the three "Supreme Cores", (Unicorn, Dragon Heart-string and Phoenix).