Istisna' is an Islamic contract where one party contracts another to manufacture a specific good, with the price being paid in installments or upon delivery. It allows buyers to pay for custom goods over time rather than upfront. The document provides examples of istisna' being used to finance the manufacturing of agricultural equipment and greenhouses. It also outlines key differences between istisna' contracts and salam contracts, noting istisna' allows for deferred payment, unspecified delivery timelines, and early cancellation before production begins.