White Walkers
Created by the Children of the Forest and led by
the legendary Night's King, White Walkers may look vaguely humanlike, but they are far from being human. Often appearing on horses, they are much taller than humans and have wispy white hair, a mummy-like appearance, and glowing blue eyes. Their presence brings a chill, and they can freeze things with a mere touch. This makes them extremely hard to battle, because they can freeze and shatter swords.
They aren't impossible to defeat: Jon Snow shatters a White Walker in the latest episode with his sword, made of Valyrian steel. Dragonglass (obsidian) and Valyrian steel are basically kryptonite to White Walkers. These supernatural beings, neither dead nor alive, are bad news.
Wights
One of the scariest abilities White Walkers have is the power to create creatures known as wights. Wights are reanimated corpses, like zombies, who are under the control of the White Walkers. The physical condition of the wight depends on what their body looks like when they're turned from a corpse into a wight. So if a body has been dead for months and a White Walker turns it, it's going to be bony and decayed. At the end of the "Hardhome" episode, the Night's King turns an entire village of Wildlings (
including this Pitch Perfect star) into wights, and since they're all newly dead, they'll retain their mostly human appearance. The big physical difference is that no matter what color eyes the person had while they were living, all wights have glowing blue eyes to match the White Walkers'. The only way to destroy a wight is to burn it, which is why Wildlings burn their dead. These guys are also bad news.
The Difference
There are a small number of White Walkers, and they possess terrifying powers. Wights are a product of White Walkers, and they're essentially undead pawns that the White Walkers use to fight their battles. Both are frightening and deadly.