Definition of bets
When we talk about betting in poker, we mean the betting rounds. We could also talk about the streets. Streets are the moments of speech that divide a hand; there are bets preflop, on the flop, on the turn and on the river. In each round of betting, all players must have the same amount of money to move on to the next round of betting. If a player refuses to pay the bet, they are free to do so, but will have to give up their cards and their chances of winning the pot.
More details on the bets
In no-limit hold'em games, it is possible to raise the betting depending on the size of your stack. In a game where the blinds are 1/2, all players will need to raise to a minimum of 2 to advance to the next betting round (the flop). If a player decides to raise to 6, they will have to bet 6 to go to the next round of betting, etc. Once all the uninterested players have folded and all the interested players have bet 6, we can move on to the flop. On the flop, the default bet will be 0, allowing everyone to check (i.e., pass or bet 0 if you prefer). As soon as a player bets, this will be the new amount to call for the next step.