Can someone help me understand the gap concept?

[Kopefire]

Basically I understand that you should have a better hand to call with than to bet initially, but I'm not sure how to apply this in practice.

It also seems counter-intuitive . . since starting hand recommendations tend to get looser as you go further around the table . .. and much of that looseness comes from wanting multi-way action to be able to draw to outs. But if you need a better hand to call with than to enter the betting with, shouldn't you set aside many of these hands?

I know I'm missing something .. or have something wrong . . .so any help with my understanding would be appreciated.