Its real I have had it since I was a little kid. Absolutely horrifying the first few times it happened to me. You wake up completely, and you can only move your body just so slightly. So sometimes you can get your eyelids open if you try very hard. Or move your finger barely. You can also make very quiet sounds. You are totally awake, you are not the least bit asleep and you are paralyzed. Over time I have learned to "jerk" myself out of it. Like I build up a lot of emotion and jerk myself real hard, trying to move and get out of it. Sometimes this works after a few times. I have to rest between "jerks". After about 5 minutes or so it goes away, your muscles are just released from paralysis all of a sudden. But it is totally horrifying when it first happens to you. It caused me to sleep with my parents for years as a child.
I don't get it nearly as much as I have gotten older but it pops out of nowhere and to this day it still scares me pretty bad.
I have never seen anybody though unless somebody is sleeping next to me and it happens then. Nor have I felt anybody touch me. I can't imagine if I saw somebody while this was happening, I would have a heart attack. It is terrifying enough without seeing a "creature" attacking you.