In the wizarding world, each magic wand is made from wood and has a magical core. Those made by Mr. Ollivander have one of three cores: dragon heartstring, unicorn tail hair or phoenix feather. Since different magical creatures live in different parts of the world, other wand makers sometimes use different core materials, such as veela hair. Mr. Ollivander classifies wands by four criteria. Three describe its physical makeup, including length, type of wood and core material. The fourth, which describes how the wand moves and bends, is more subjective.
Finding a wand that works for a particular witch or wizard is largely a process of trial and error. However, elements used in the wand often reflect its owner's traits. For example, the types of wood used in the wands belonging to Harry Potter, Hermione Granger and Ron Weasley correspond to the trees associated with periods of the Celtic year. It's a little like a horoscope -- each character's birthday falls within a certain period, which corresponds to a specific tree. Harry's wand is holly, Hermione's is vine wood, and Ron's is ash.
The woods used in other wands can also reflect their owners' personalities. A wand made from rose wood and veela hair, possibly the most feminine wood-and-core combination possible, belongs to part-veela Fleur Delacour. Wood from a yew tree, which has poisonous sap and foliage, surrounds the phoenix-feather core of Voldemort's wand. A mighty, protective oak contributed the wood for half-giant Rubeus Hagrid's wand. Since holly keeps its green leaves all year and displays bright red berries in winter, some people see it as a sign of hope. Holly is also said to ward off evil, and it's part of Harry's wand.
The affinity between the type of wood and the person who wields it may be one of the reasons why witches and wizards can have less success with others' wands. It's certainly possible to use another's wand in a pinch. Barty Crouch, Jr. created the Dark Mark with Harry's wand, and Peter Pettigrew used Voldemort's wand to cast Avada Kedavra, the killing curse, on Cedric Diggory. Neville Longbottom used his father's old wand until his fifth year at Hogwarts. However, witches and wizards have the best results with the wands that chose them.
Wands have some magical power of their own, and in the hands of the non-magical -- Muggles -- they could be dangerous and unpredictable. But their primary role is to act as a focus for the abilities that witches and wizards already possess. For this reason, witches and wizards become completely familiar with their own wands. They can recognize their own wands immediately and can sometimes match other wands with their owners with little or no thought.
But sometimes, no matter what his intent, a wizard's wand will not function the way he expects it to. We'll look at why in the next section.