What exactly does under contract means in real estate .

It means that a contract has been signed between a seller and buyer but it hasn't closed yet. The parties are waiting for contingencies to be satisfied, inspections to be performed, the title search to be completed and the requirements of the loan commitment to be fulfilled. When all of this has been done and the lender has given their approval then there will be a closing, where the deed and money are exchanged and ownership changes from the seller to the buyer.