Right, now I see what you are saying.
It's like this. If you have a weak made hand, and you bet, any decent hand, which most likely has you beat, will at least call, and maybe raise. A hand that has no showdown value at all will mostly fold.
If you have a weak made hand and you check, that same hand may check behind. If it does bet, you can then decide whether or not to call yourself.
The advantage of doing it this way is, your opponent, who would fold his weak hand to your bet, may be induced by your check to try a bet with his weak hand, which you can then call. This is called the bluff induce. You don't bet with your hand, and try to get opponents to make a bet that you have some chance of beating if you see a showdown.
So, when you bet with a weak hand, the only time anyone will call, or raise, is when you are beaten. You will lose every one of these bets. Whereas, if you check, a weak hand will either check behind, giving you a chance to win the showdown without having to put any more money in, or bet, allowing you to pay the same amount of money without risking being raised. Since this bet may be a bluff by a weaker hand, you will win more often, without risking as much to do it.
I think.