Pot odds are just the ratio of the current bet to size of the pot.
If you have not yet made your hand (e.g. only 4 spades) then you consider your drawing odds, which is the chance of making your hand.
But say there is a pair on the board. Then you need to consider the probability that your opponent has or will make a full house, which would beat your flush if you were to hit. Likewise the probability that someone will have a higher flush than you.
Analyzing this in aggregate is what gives you the expected value, which is what poker players consider.
If you are simply playing a cash game with unlimited buy-ins. Then assuming your overall bankroll is sufficient, you will always make plays with positive expected value, even with high variance, because it is a continuous game and you expect the total return to be positive over sufficient iterations.
If you are playing a tournament with a set number of places in the money, then you need to take into account the variance as well as the expected return because it is an episodic game and the types of plays you will make will depend on not just expected value of the single play but what place you are in currently and the number of players left.
And probably the most difficult to estimate are the implied odds. If you do make your draw, how much money can you expect to make in later betting rounds.
Implied odds are interesting in that they can make very bad hands more playable because if you do hit, then the likelihood that your opponent believes that they are winning is higher (because the chances of such a bad hand being played rather than folded immediately should be low) and thus the probability that you can elicit more money from them is higher.
Small pairs and low suited connectors are good examples of these kinds of hands. Your pre-flop chance of winning with a pair of 2's on a full table is pretty low. But if the flop is 2-K-A, you will likely get a lot of action.
If you have not yet made your hand (e.g. only 4 spades) then you consider your drawing odds, which is the chance of making your hand.
But say there is a pair on the board. Then you need to consider the probability that your opponent has or will make a full house, which would beat your flush if you were to hit. Likewise the probability that someone will have a higher flush than you.
Analyzing this in aggregate is what gives you the expected value, which is what poker players consider.
If you are simply playing a cash game with unlimited buy-ins. Then assuming your overall bankroll is sufficient, you will always make plays with positive expected value, even with high variance, because it is a continuous game and you expect the total return to be positive over sufficient iterations.
If you are playing a tournament with a set number of places in the money, then you need to take into account the variance as well as the expected return because it is an episodic game and the types of plays you will make will depend on not just expected value of the single play but what place you are in currently and the number of players left.