Is it the same thing as alternate picking almost? the lesson didnt really give me a better understanding. I would like to know the difference with theses two.
Tremolo picking is picking a single note so that the picking sort of blurs the note. It is used in place of simply letting the note ring out in some cases to build tension in a song (not your arm, of course) and/or to sound cool. Alternate picking is used in tremolo picking (it's hard to tremolo purely down or up strokes), but they are different techniques - alternate picking is simply alternating up and down strokes of the pick.
It helps if u use the side of your pick to do tremolo picking, its faster
The difference is that "tremolo" is an effect, whereas "alternate picking" is a technique.

Alternate picking is used to create a tremolo effect- but this is only true for instruments that are played with a pick.