Hi and welcome to FTR!
pot odds theory isn´t that hard to understand. basically your just calculating if your getting the right price to draw.

say you hold
AhTh in the BB, its folded to SB who calls. SB bet 100 on the flop and you call, pot contains $300

board is
2h 8h Qc 5h

there are 46 cards left unseen, the nine remaining hearts will give you the winning flush, 9/46 or ~20% of the time. in odds format its about 4 to 1 against making your flush.

first scenario: SB bets $300, offering you to play for 600 (pot+his bet) for the price of 300, giving you 2:1 on your money. since you´re a 4:1 underdog you should fold.

second scenario: opponent bets $100 on the turn, now you´re getting 4:1 on your money and you will break even in the long run making the call.


its a quite simple example, but you´ll get the picture? if the pot offers you better odds (pot+bets/raises/calls:your call) than the odds against making your hand (cards unseen:your outs) you´ll make money in the long run et vice versa.