Significance of "in contract"

It means both parties have signed the contract and it would be hard for either to back out without paying some sort of damages (i.e., giving up the deposit). I would be very surprised if any broker would show you such an apartment, let alone allow you to make an offer. If I were the buyer of such an apartment, I would be livid if I heard the apartment was being shown and if I were the seller, there would be no need for me to show it. The deal could fall through, but my guess is you need to wait for that to happen.

o.k., thanks. I've watched one particular apartment here which was "in contract" 3 months ago, then it was available again, then "in contract" again. So I guess the first deal fell through..
There's another condo I would be really interested in which is "in contract" for 4 months now - I figured there might be some problems and it's worth to wait if it comes back to market.
Or is this a normal period of time until "contract signed"?

"in contract" means that the contract has been signed by both parties. Generally things don't fall out of contract often particularly given the increasing rarity of mortgage contingencies. I wouldn't hold your breath for a condo that has been "in contract" for 4 months--it is very possible that the agent forgot to update the listing to "closed". Shoot the broker an email and ask if it is closed yet, but concentrate on active listings...

Good advice but if you love the place be SURE to let the listing broker know of your interest. My husband and I live in a house that was "in contract" that fell through. We swooped in and boy were they glad to hear from us!