newbie question

Im 20(obviously I have no experience) So this may be a dumb question but Ive tried to do some searches and look into the saved threads and didnt really see anything on this topic exactly.
I read a lot about people saying they are becoming an O/O but then they ask what company they should go with. If youre an O/O then why do you need to have a company to work with/for? What are the pros and Cons?
My understanding was that if youre an O/O then you can find your own loads and attempt to make your own company.
Also one more question. I see guys saying they average about $1.50 a mile on a load. Are these the guys that are an O/O within a company? because I just dont see how you benfit that much more making $1.50 a load but at the same time I see companies with mutliple trucks so I am ASSUMING that those guys who are O/O making $1.50 a load are having their prices cut by those companies?
I dont know, maybe I am being completely ignorant but I am very curious about this topic.