How do Firms in Competitive Industries Make Money?

Although I have spent a lot of money on this MBA, pretty much all I need to know I could learn from The Real Housewives of Orange County (fine, so I've watched it once or twice, Jo is hot!)

Anyway, Lindsay, one of the young ladies on the show (whose father wants her to go to "Princeton, Harvard, or Yale") when asked in an interview for a job as a receptionist...at a...hair studio...in a mall how she feels about retail sales, breaks it down Porter's-Five-Forces style:

"Yah...I think retail sales are good. They are good for making money and giving people stuff."