Immobilized?

[A Flannel Shirt]

So I'm looking at Improved Force Stun and it boils down to Immobilize the target for one round.

I went searching for what that exactly does and I can't find it.

I know what it literally means but what does it do for game purposes?

Deny a move action, swift action, standard action, or all the above?
What about being flat footed or denied reflex bonus?
Reactions? Block, deflect, negate energy?

Thanks