Definition of "bet
When we talk about the bets in poker, we mean betting rounds. We could also talk about the streets. The streets are the moments of speech that divide a hand; there are bets preflop, at flop, at the turn and on the river. In each round of bets, all players must have bet the same amount to move on to the next round of bets. If a player refuses to pay the bet, he is free to do so, but must give up his cards and his chances of winning the prize pool.
More details on the bets
In Hold'em games without limits, it is possible to raise the bets depending on the size of our mat. In a game where the blinds are at 1/2, all players will have to put at least 2 to move on to the next bets round (the flop). If a player decides to raise to 6, he will have to put 6 to move on to the next bets turn, etc. When all the players who are not interested have folded and all the interested players have put 6, we can move on to flop. At flop, the default bet will be 0, which will allow everyone to check (i.e. pass or bet 0 if you prefer). As soon as a player places a bet, this will be the new amount to follow to move on to the next step.