Root effects are a form of crowd control that cause the victim to be locked in place and unable to move. A root effect differs from a stun effect in that the target is still able to use abilities, spells or melee attacks, but cannot move from its location as long as the effect is active.
Examples of abilities that can root opponents:
- Druid:
[Entangling Roots] - Mage:
[Frost Nova] - Hunter:
[Counterattack]
Additionally, talents such as 
[Frostbite] and Improved Wing Clip give some abilities the potential to root an opponent.
See also: Crowd Control, Charm, 
[Dazed], Fear, Sleep, 
[Slow], Snare, and Stun.