Hey, I'm Nicky Numbers, professional poker player and now we're going to talk about betting. Betting can only occur post-flop, on the flop, turn, or river. It cannot occur pre-flop because the bets have already been done. The blinds are forced bets. You only have the option to make a bet when you're first to act post-flop or when your opponents check to you. Once someone has already bet then you have the option of folding, calling, or raising. If you want to make a bet then you'll obviously have some chips in front of you. You can state your wager by saying the amount you want to bet, like "make it 15" and toss out three red. If you state the amount first, then the dealer will make sure that the number of chips you put in matches that amount.
If you just make a bet by putting the chips out first and not declaring anything, then however many chips you put out there is the bet size. You cannot go back to your stack. A bet is going to be physically indicated often by moving it somewhat significantly past your cards. So say I want to bet this entire stack of red chips, I would move it forward past my cards. In many poker rooms you may find a betting line, which is a line drawn on the table whereby if you cross that line, those chips are now your bet amount. Or, before touching or even moving chips you can state the bet. Like, "I bet this" or "make it 15 to go". Now let's say there's a big pot out there.
A bunch of chips just in the middle. Whenever you're making a bet, you want to make sure that you're never letting your chips go anywhere close to the pot. So if I bet 15, I don't want to do this. That's called splashing the pot and it's really bad etiquette. It confuses the amount you put out there with the amount in the pot. If you're not going to state your bet amount verbally, then whenever you're putting chips toward the pot make sure you take an extra moment and pause to count the chips before you put them in just to double check, because the dealer won't be able to help you once you release them. After you bet, your opponents can call, raise, or fold. If they all fold, then you win the pot uncontested, which means whether you're on the flop, turn, or river, because you have no opponents left in the hand you just win, without ever having to show your cards. If your bets are called all the way down through the river, then a showdown occurs.
If you're on the flop or turn and choose not to bet, and you're last to act on that street, then you'll see the next card for free by also checking. If you're on the river and you make a bet which is called, then you and your opponent will expose their hand, and the best hand will win. If your opponent raises your bet, then they are increasing the wager and forcing you to put more chips into the pot in order to continue. If you don't do so, then they may win the pot uncontested when you fold. If they elect to raise, action will then go back to you and you'll have the option of calling, folding, or raising as they did when you bet. And that's how you bet in Hold 'Em.