The poker betting structure 

There are different types of betting structures in poker. In all structures a raise must be at least as high as the previous bet or raise, unless a player is going All-in.

Fixed Limit
In Fixed Limit poker games, bets and raises are set at a fixed amount, Small bet and Big bet (ie. In a €2/4 game, the small blind is €1 and the big blind is €2. On the first two betting rounds, the raise is €2, and on the last two, it is €4). The maximum number of bets that can be made in one betting round is 4.

Pot Limit
In Pot Limit poker games, you may raise any amount up to the size of the pot. This includes bets in front of you plus your call. For example, if there is €2 in the pot and you are the first to act, the maximum you can bet is €2. But the next player could then call that €2 and raise an additional €6. The minimum bet equals the size of the big blind or the size of the previous bet or raise.

No Limit
In No Limit poker games, you are allowed to bet any amount at any time. The minimum bet equals the size of the big blind or the size of the previous bet or raise.

All-in
A player goes all-in when he/she either makes a bet/raise for all his chips or a call for all his chips. You may run out of sufficient chips to bet or call in the middle of the hand. Don’t worry, you can then go all-in and all the money you invested so far will be separated into a special pot. You will remain in the game, but there will be no more betting or calling for you. If other players continue betting, all those bets will go to a side pot that only they are eligible to win.

An Example
Let's look at an example of going all in. Before the flop, everyone bets €2. Then, Peter and Anna bet a total of €4 each. You go all-in and bet only €3. That means you can only win €15 (€3 from Peter and €3 from Anna in addition to the €6 already in the pot). There is now a main pot of €15, which everybody can win, and a side pot of €2, which only Peter or Anna can win.

 Peter bets
You call
Anna raises
Peter calls
You go all-in
Main Pot
Side Pot
Show the round again