There are several types of sukuk discussed in the document. Istisna'a sukuk involve project financing where funds are advanced for supplies/labor and repaid from project revenues. Salam sukuk involve the purchase of commodities on a deferred delivery basis, with full payment up front. Ijarah sukuk involve the purchase of tangible assets by an SPV from an originator which are then leased back, with rental payments funding returns to sukuk holders. Mudharabah and musharakah sukuk also exist but are not described in detail. Each structure aims to comply with Shariah principles while providing financing.