The best way to describe it is this: Force your opponent to make incorrect calls or folds mathmatically...in other words if you hold
10♥J♥ in the big blind Preflop and your opponent holds A♠A♦ on the button. you call his 2x bb bet (because you're getting extremely good potodds to do so.. lets say its 1/2 NL and there is now 24$ in the pot
The flop comes Q♥K♥A♣
He flopped top set, and you flopped the nut straight, with redraw to a flush, and 2 outs to a Straight flush.
If your opponent knew your hand, he'd most likely fold his trip Aces, because he's now an underdog to the nut straight with redraws to the absolute nuts (ace of hearts would be absolutely devistating for him). His only wins are a King, a Queen, or a running pair on the turn and river... and we can probably discount some of his outs because the other people in the hand are somewhat tight players, and won't call a raise with any hands except suited connectors OR any two face cards.
So, What do you want your opponent to do on the flop betting? You want him to make a mistake that he wouldn't normally make if he knew your hand, in otherwords, you want him to call (or even better yet, raise) your nut straight with the second best hand of a set of aces. Every time he does, you gain..even if a miricle running pair, or the K♦ shows up on the turn or river, you still have gained on this play. Compare this concept to pot odds. You know that you're a 11-1 underdog to make your gutshot straight, but if the pot is offering you 22-1 odds, you are actually making money if you call in that situation each time. If there is 22$ in the pot, and you have ot call a single dollar to see the next card you're going to lose 10 times and win once. You're going to lose 1 dollar 10 times and win 22 dollars once, for a net gain of 12 dollars. This is the same thing in the Fundemental therom of Poker. The money your opponent looses by making the incorrect call has to go somewhere...and that somewhere is you...while you may lose the pot, you've stilled gained anywyas. Here's why..
You have 2♦2♠ on the button. There are 3 limpers to you, you limp, the small blind folds and the big blind checks. The same 1/2 NL game you were in before. 10$ pot (the smallblind is taken out for hte progressive badbeat jackpot) The flop comes 2♥7♥K♠ Checks to a guy in Middle position who bets 5$. The guy to your right folds and you put in a raise to 35$ hoping to win the pot right there. it folds around to the original better who you have correctly put on a flush draw. He now faces the dilimma to call 30$ to win 50, or 3:5 pot odds for his flush he's roughly going to make 1 in 4 trys. His odds aren't good enough to call, but he may do it anyways (and you want him to call you). For simplicity lets assume that bet put him all in,as to discontinue any further betting, and for easier math on my part, assume that the pot is now 100$ (160 after his call) He's going to lose 60$ 3 times and win 100$ once. For a net loss of 80$. So, even if the river is a heart, you can be sure that in the same situation, given the same opponent, if he makes that call it will eventually be a 80 profit to you.