Standard limit games have a cap at 3 raises.
For example, a £1/2 limit game, blinds are £1 and 50p. The maximum you can bet, or be asked to bet by other raisers in the first two rounds of betting is £4 (the forced £1+3 raises). The maximum you can bet in the 3rd and 4th rounds of betting is £8. A minority of sites will have one more raise per round, and a minority will allow limitless raises if two players go to the showdown, which is sneaky because when that happens it usually means both players have the same nut hand, and both lose out when the pot is first raked, then split back to them.
Pot Limit and No Limit are different. No limit does what it says on the tin, and you can bet up to whatever you've got in front of you at any point.
Pot Limit is more complicated in that you can only bet what is already in the pot, though note that when determining what this is, your call of the existing pot is counted in the total permitted raise. Again using the £1/50p as blinds, a player wanting to 'raise the pot' first calls the £1 BB bet (making a pot of £2.50) and then bets the £2.50. If the next player now wants to raise the pot (which is standing at £5) he may first call the £3.50 bet (making £8.50) and may then raise a further £8.50. Very complicated thinking about odds etc in pot limit, which is why many non-experts (me included!) treat it basically as a no limit game.
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