What is this sleep/dream 'paralysis' phenomenon called?

Some days ago, just seconds after I fell asleep, I started to dream a pretty violent dream.
In short, I was attacked by two vicious dogs.
Fortunately I was in such a sleep state that I could decide to get out of that dream.
Then the following happened : I was wide awake but was not able to move any limb or any other muscle for that matter and had the feeling that someone pinned me down.
Couldn’t speak or turn my eyes and was quite in panic.
It ‘only’ lasted for about twenty seconds.
Is there anybody who knows what happened to me?
Maybe can supply me with some information /websites?