Comment by TZubiri

By posture do you mean act verbally and physically? Or bet as if you had a good hand?

The first is mostly inconsequential in poker, you should avoid having tells in your posture and speak, but the goal is to avoid conveying information about your hand, not conveying false information about it to deceive.

The second is just the game itself, acting as if you had strong cards has a cost, and is not lying, when you bet you are not saying "I have a hand". In a sense you may bet with a bad hand, but you are more forcing your opponent to pay for a chance to win the pot on account of your hand potentially containing a strong hand. You are truthful in your representation of a potential strong card.

In fact if you were to bluff on a situation were you could not ever have held a strong hand, it would be a mistake, and you would stand to lose expected value.