The types of effects are, as defined by Blizzard - the ONLY authority on this matter:
"Stun" - Prevents you from taking any action, but allows you to take damage.
"Incapacitate" - Prevents you from taking any action, but breaks if you take any damage.
"Snare" - Slows your movement speed, but still allows you to move and act at reduced movement speed.
"Root" - Slows your movement speed to zero, holding you in place. You are still able to act but cannot move.
"Snare" and "Root" are the ONLY two effect types in the game that are classified as "movement impairing" effects. Note that this has NOTHING to do with the varied english language definitions of the phrase "movement impairing", this is a definition of a term in the World of Warcraft.
Check out the long old debate, that finally died some time ago, about Judgement of Justice not being a "movement impairing" effect (since JoJ doesn't impair speed below 100% it was not classified as such). It doesn't matter how YOU define your movement as being impaired - it's a game mechanic and Blizzard has decided this is how it is.