[numeri]

Here's a hypothetical situation:

Both villains here are loose and passive - they'll call down with any pair and don't raise without a very strong hand.

We have A[img]/images/graemlins/diamond.gif[/img] A[img]/images/graemlins/spade.gif[/img] in MP.

Preflop: folded to us, we raise, folded to the blinds who both call.

Flop: (6 SB) 5[img]/images/graemlins/club.gif[/img] 9[img]/images/graemlins/club.gif[/img] 2[img]/images/graemlins/diamond.gif[/img]
blinds check, we bet, they call

Turn: (4.5 BB) K[img]/images/graemlins/spade.gif[/img]
blinds check, we bet, they call

River: (6 BB) T[img]/images/graemlins/club.gif[/img]
blinds check, we bet, SB calls, BB check/raises, <font color="blue">we fold</font>

We're not obligated to call a river raise or check/raise. We need to bet here because both villains will call with a pair - we miss out on a ton of value if we check behind.

There are lots of other situations, of course. I hope this gives you an idea of what we're talking about.