When you start learning guitar, picking style is one of the most important things to think about, because it will always be with you. Once you learn it - you don't want to re-learn it! So it's best to try a couple of styles, see which one works best for you and master it!
In the video you can see how basic 3 styles work, and the rest are just variations:
Style 1: the advantage of this style is complete freedom of your right hand movements. You do both picking and muting of the strings you don't play, at the same time. One of the variations of this style is letting your fingers out of the fist and this variation is most common for riffing.
Style 2: some people find it really good but it didn't work for me, although I did spend over 1 year playing like that. Muting is somewhat difficult when playing like that but you can see shred master Michael Angelo Batio picking like that and achieving monstrous technique and speed.
Style 3: you can see that style and variations of it pretty often. One of the examples is Luca Turilli of "Rhapsody Of Fire" who is a very skilled guitar player - he uses this particular picking style.
In our next lesson you'll be able to apply these picking styles to a simple alternate picking exercise and see which style is most comfortable for you! It's really important to decide early which style is best for you so our next lesson will help you to do that.