2 outs would be for anyone trying to turn their pocket pair into 3 of a kind, 3 outs if you already have a pair and are trying to make 2 pair (using ONLY your hole cards), 4 is an inside straight draw or their 2 pair into a full house, 8 is an open ended straight draw, 9 is for a flush draw, 12 would be for an inside straight draw completing to EITHER a straight or flush, 15 is an open ended straight flush draw completing to EITHER a straight or a flush.
All odds against are to 1. For example if you have 1 out in the hand and are trying to figure out your odds against all the way to the river you are 22.5 to 1. In other words you are going to have to play this exact same hand 23.5 times for you to win once.
Odds against are used to figure out Pot Odds. Pot Odds are the ratio of potential winnings compared to the cost of your call. Use this mathematical formula. Money in Pot divided by Cost To Make The Call. Let’s say there is 500 in the pot and the cost for you to call is 200. 500/200=2.5. You would only want to call this bet if you had 14 or more outs because the Odds against those hands are less than 2.5. Fold anything with greater odds against than the number you determined by using this formula.
Are you a fan of percentages as opposed to a fan of x to 1 odds? Use this formula instead. Cost To Call divided by (Money In Pot + Cost To Call)
multiplied by 100 equals the percent chance your hand has to win to give you the proper pot odds to call. 200/(500+200)=0.285*100 and we have 28.57%. Fold any % that is less than the percentage you determine with this equation.
You should figure pot odds only for the incoming card. Pot odds must be redetermined on every incoming card. Never try to figure out pot odds for both turn and river percentages because your opponent will have the opportunity to make the hand more expensive for you to call the river on the turn. Your draw may be affordable to see a turn but not the river.