The poker theorist and great fan, David Sklansky, who coined the term Semi Bluff”a bet with a hand which isn’t the best hand but has a reasonable chance of outdrawing those hands that initially called it. The Semi bluff has to pros unlike the regular bluff which has one depending on the method. Free  money internet poker there is no such thing, unless you learn to semi bluff.

-The opponent might think the blugger has the hand he’s representing and will release his own hand.

-If the opponent calls the blugger might catch the card he needs and beat his opponent that.

So the opponent is caught in two minds and will regularly give up and release.