Where does our edge come from?

There are 3 main ways to get advantage over your opponent in poker:
- skills
- cards
- position

More skilled player is going to win money from less skilled player over the long run.
If your hole cards better then your opponents you obviously have an advantage.
If you have position on your opponent you can see what he does before have to act and this gives you advantage on each betting street.

How to use this knowledge in game?
For example you are in BB with marginal hand. It’s folded to loose, aggressive player OTB who open raises. SB folded. Should you fold? You have positional disadvantage, but you think that large percentage of time LAG player will have cards weaker then yours, so you have cards advantage. So it boils down to skills. If BTN is a good player and you don’t have big skills advantage over him it’s better to fold. But if you think you much better then him, then it’s possible that you can make profit from playing your hand.
Another example is that sometimes you can find yourself in such a great game where your skills advantage over other players is so great that you can profitable play almost any two cards from late positions. Your skills and positional advantage allow you to overcome your cards disadvantage.