Understanding Petetonics

I am new to GMC and even though I understand most of the beginner lessons I do not understand the petetonic scale and soloing/improvising. I would appreacate if anyone could explain petetonics as if they were talking to a baby that would be great. Also the thing I cant figure out most is root notes, I just need to know what they are and what they do, and how to use them. I also would like any links to videos explaining these things for my level guitarist. I think this will not only massively help me but will help others with this problem. Thanks for any help, its all greatly appreciated.