Bluffing is an integral part of poker
For example, if you have two spades at casino games in your hand and you get bottom pair on the flop and are four spades to a flush, making a decent bet here is what we would call a semi-bluff. You probably do not have the best hand right now, but you have a hand and a chance to have a really good hand that will most likely win you the pot in another spade hits the board.
By using a semi-bluff instead of bluffing with absolutely nothing, you increase the chance that your 'bluff' will be successful even if your opponent does call. Not only will this be a great way to get comfortable with the idea of bluffing on poker strategies but it will also make the other people at the table more conscious of your presence at the table. Win a few hands where people think you are bluffing and it turns out you had the best hand, they will be less likely to call when you really start bluffing.