Part of what makes bets on the flop and turn so effective in Texas hold'em is the threat of future betting. Players who call bets at these stages of the hand (especially those out of position) know they could face even larger bets later in the hand.
Here's an example of what I'm talking about. Let's say that we've reached the turn in a hand and the board is 
. The pot was built up to $150 with a raise and some calls before the flop. The initial raiser bet $50 on the flop and you were the only caller with a 
. So now the pot is $250 on the turn and the initial raiser checks. You probably have the best hand here, but there is also the possibility that the leading bettor is scared of this board, which keeps getting worse for a player holding a hand like K-K or A-A. In this spot, you could make a big bet and may take this pot down, for not only are you making a sizeable bet on the turn, but your bet is a threat of an even larger wager on the river.
This follows a concept known as reverse implied odds. As you probably know, implied odds are a consideration of the money you could make if you hit a draw. You may call $100 on a straight draw hoping you can win $1,000 if you hit. The concept of reverse implied odds is risking a large amount to take a chance of winning a smaller amount. In the example above, you are giving your opponent reverse implied odds. If you bet big on the turn, he may think he will have to call that bet and one more big bet on the river, so in order to win the $250 currently in the pot, he may have to put triple that number in before the hand is over.
Of course, you don't have to bet on the river if you think you may be beat, but your bet on the turn does turn up the heat. Your opponent may think you have the best hand or be betting a draw, but if he's unsure he's in a tough spot on the turn. That's the problem with giving up the lead. By checking the turn, he gave you control of the hand. If he was unsure whether or not he was ahead, he should have bet another modest amount like $75 or $100. The pot is too big to just give up on so easily. Then again, if he only has ace high he knows he's probably beat and folding anyway.
This concept is why bluffing on the turn is much more effective than bluffing on the river. If you bluff on the river, then your foe only has to call the size of that bet to see if you really have a made hand. If you bluff on the turn, then your opponent must call that bet with the threat looming of a larger bet on the river. Depending on the size of your stack, that could be a scary concept.
*Play online poker, practice your skills in free money games, play free rolls for opportunities to win real money, and join the world in a game of poker. Be sure to join in the quest for a seat in the PokerNews Cup , you won't want to miss this event.*