Read rules of hold’em and learn that game before playing pineapple, for it is a variation of hold’em.  Similar to hold’em, Pineapple has a flop, turn and river.  The game can be played in a no limit, limit and pot limit fashion.  The difference in pineapple is each player is dealt three down cards instead of two.  In regular Pineapple, one card of player’s choice is discarded before flop and in Crazy Pineapple the card will be discarded post flop.  Betting remains the same as in hold’em and at showdown the player may use the remaining two cards in hand to create the best five-card hand.  A player with three hole cards at showdown will result in a dead hand. 

 

Pineapple

So Pineapple plays the same as hold’em, but each player gets 3 down cards and one card gets discarded pre-flop.

 

Crazy Pineapple

Crazy pineapple on the other hand gives the option to discard one hole card later in the hand and tends to be played in hi-lo, eights or better format.  A player can use any combination of cards on board and in hand to make the best five-card low and high hand.  If no low hand is made then the high or best hand will take the whole pot.

Here are examples of low hands, assuming you already know of the high hands.
5-4-3-2-A (five high or a wheel)
6-4-3-2-A (six high, any five unpaired cards six being highest)
7-6-5-3-A (seven high, any five unpaired cards seven being highest)
8-7-6-3-2 (eight high, any five unpaired cards eight being highest)