See the post on Table Stakes to see the most you can win or lose in a hand based on how much money, or how many chips, you have “in play”(the amount of money or chips you have on the table in front of you).
No limit betting can apply to any game of poker. Texas Hold’em is almost universally played No Limit, especially in tournaments. There are also Spread Limit, Structured Limit (also called just Limit), and Pot Limit variations.
In no limit, if no one has raised in front of you, the minimum bet or raise is the amount of the Big Blind (which is considered a bet). The maximum amount you can raise to, or bet, is the amount of chips you have in play (all in). You can also bet any amount in between.
If someone has raised before it is your turn there are a couple of variations, depending on the card room.
Let’s say you have $100 in play and you are in a cash game with blinds of $1.00 and $2.00. You are “under the gun” (the person to the left of the Big Blind and therefore first to act) so your options are to fold, call $2.00, or raise to any amount between $4.00 and $100.00 (all in).
Now, let’s say everything is the same but you just call the $2.00. It folds around to the button, and they raise $8.00 for a total bet of $10.00. The Small Blind and Big Blind both call. Now your choices are to fold and lose the $2.00 you have put in the pot, call the raise and add another $8.00 for a total of $10.00, or raise. If you call the raise, the betting round is closed since the next player to act is your opponent that raised. They cannot raise their own raise, and no one after them raised.
In most card rooms the minimum raise you could make is the same amount that was raised to you, in this case $8.00. A min(imum) raise would then be a total of $18.00. Your initial call of $2.00, plus the button raise of $8.00, plus your re-raise of $8.00. In a very small number of rooms the smallest amount of your raise is the last “full bet”, or $10.00 here. This would make your raise to $20.00. We will use the normal one for the rest of this discussion. The most you could raise is to $100. If you raise to $18.00, or any amount above that but less than your all in, you have made a “full raise”, which opens up the betting for your opponent to raise you again. A full raise is the minimum allowable raise if a player has enough chips. In the case of someone going “all in for less” different card rooms have different rules. Keep reading for more.
If someone makes a full raise to you, you have the option to fold, call the raise, or re-raise again. This can go back and forth as many times as you wish until everyone is all in. There is no maximum number of raises.
Let’s look at a scenario with a “less than full” raise. Seating is as above. You open raise to $10.00, the Button and Small Blind call, and the Big Blind goes all in for $12.00. Since this less than the full raise of $8.00 and is only a $2.00 raise over your $8.00 raise, your only options are to fold or call the $2.00. It does not open you up to raising again as it was not a minimum legal raise.
At any point when you are first to act, or someone has made a full raise in front of you, you can go all in for your entire stack. If anyone calls with less you can win their full stack. You cannot lose your full stack when you have more than everyone else in the hand.