Deceptive plays are those where a player takes actions OTHER than StraightforwardPlay. The idea here is to deceive your opponents about your true holding, thus making them play incorrectly against you.
A bluff is a deceptive play which pretends you have a strong hand in the hopes that your opponent will fold.
A value bet with a strong draw is deceptive because you are betting without a made hand. If the draw is strong enough and is called by enough opponents, the bet has value.
Checking with a strong hand with the intention of raising later is also deceptive.
A bet or raise from late position can intimidate other players, leading them to check to you in a subsequent round. This is called a FreeCard play.
It should be obvious that most deceptive plays involve playing your hand incorrectly. Failing to bet a good hand is wrong; betting a weak hand strongly is wrong. The deceptive play is only warranted when the net result is likely to result in a better profit.
For example, if you have a very strong hand and a bet now is likely to cause the entire field to fold, there is not profit in betting. But a SlowPlay will give your opponents' hands time to improve so that they will either call or bet themselves. Note, however, that if they would have called in the first place, the deceptive play is unnecessary, and probably wrong!