In no limit Hold'em it is sometimes profitable to call a small raise with marginal cards, to see a flop, if your call cannot be reraised. If you hit the flop, you have a good chance of de-stacking your opponent, with a well disguised hand. A situation similar to the "Protected Pot" occurs if there are several limpers before you. Most players will not raise without Aces or Kings. Even players with Queens would rather see the flop cheaply and they really don't want to reopen the betting for early limpers to reraise. This "Protected Flop" allows you to limp in with hands that should otherwise go into the muck. The multi-way action not only gives you better pot odds for the marginal play, it also gives you an almost perfect read on in subsequent raise, by players yet to act. You can either call a small raise with high implied odds or muck your hand with high confidence that it was the correct play.
Let's look at a couple of examples.
You are in a tournament with a medium stack after the first break, in 8th position. Two players limp in front and you pick up 10-8 suited, a very marginal hand with four players yet to act. If the UTG opponent and the Button haven't been super aggressive, you can probably limp into the pot with high confidence that it will not be raised. If it is raised, you can put the raiser on a very limited range of hands, and probably call a small raise if the implied odds are large. If you miss the flop, you muck the hand. If you hit the flop, you are in great position to take your opponent to the felt. Later in the tournament when short stacks become desperate you should always use caution because they are prone to push all-in with only marginal cards, but those marginal cards are probably better than yours.
In a cash game or during the rebuy period of a poker tournament, this type of play can be even more tempting, since you can always rebuy if things get out of hand. In the cutoff with three limpers, you pick up J-10 off suit. (One of the hands I love not to play.) Now you can limp in, or even try a small raise. If reraised, muck it. If the flop hits you, you are in great shape. Otherwise you muck the hand. I wouldn't be to proud of top pair in this situation and top two pair might be quite vulnerable since that puts two cards two a Broadway straight on board. Many people play K-Q and you have had several limpers. Just be cautious. Play big pots with big hands and your hand isn't big yet.
We often talk about varying your play. The protected flop is a situation where you can often, safely, vary your play. In any situation involving marginal cards, you must be willing to abandon the hand to significant action. It also doesn't mean that you make the play at every opportunity but it does allow you to play some very marginal cards from a relatively safe position, and it will drive skilled opponents crazy when you bust their premium hand with a couple of rags.