Rationale: these statistics are essential for deciding whether to fold or play a draw.  Paying to see more cards requires sufficient pot odds.  That is, there has to be more money in the pot than the odds against completing the hand.  Filling an inside straight is 11:1 against, so the pot needs to have in the vicinity of 11 bets in it to justify calling.  (Exactly 11 is unnecessary, because the pot will probably grow some more. See implied odds.)  Hands such as two pair or a set (i.e. three of a kind) often win without improvement, unless the raising is heavy, in which case you need to know the chances of hitting a bigger hand. 
      The table provides odds for one card to come rather than two, because the pot odds have to justify a call at each street.  With two cards to come, odds for an inside straight are about 6:1, but you will likely have to call at least two more bets, so your decision should be based on 11:1.
   The flush and straight draws assume you have four cards and need just one more.

Definitions: flop, open ended straight; inside straight; pocket pair; over cards; set; pot odds.