I don't know all the details because I'm not a math / business major (I prefer dead things, archaeology), but there is a problem with 2 ice cream vendors on a beach.

Whole beach is 1 mile long. 2 vendors. They set up in the middle, and make more money with their stands next to each other, than if they're stands were on opposite ends of the beach. Has to do with lines, waiting and selection. Vendor 1's line is too long, so people go vendor 2 who has the shorter line. Vendor 1 carries a couple of things vendor 2 doesn't, vice versa. At least that's how it was explained to me, or close enough.