Salam contract in simple terms

It would be helpful if you can explain what is salam contract in simple terms.

Salam contract is one of the most common sale contracts. According to the Salam contract, you can carry out a sale whereby the buyer agrees to pay the price in advance. And the buyer expects to receive the commodity when it is delivered at a future specified time by the seller. In Salam’s contract, the seller gets a moral obligation to provide the goods at a future date. You can not cancel the salam contract once you sign it.