Structured Investment Vehicle
It is a pool of investment assets that attempts to profit from credit spreads between short-term debt and long-term structured finance products such as asset-backed securities (ABS). Funding for SIVs comes from the issuance of commercial paper that is continuously renewed or rolled over; the proceeds are then invested in longer maturity assets that have less liquidity but pay higher yields. The SIV earns profits on the spread between incoming cash flows (principal and interest payments on ABS) and the high-rated commercial paper that it issues. SIVs often employ great amounts of leverage to generate returns.
Also known as "conduits".
SIVs are less regulated than other investment pools, and are typically held off the balance sheet by large financial institutions such as commercial banks and investment houses. They gained much attention during the housing and subprime fallout of 2007; tens of billions in the value of off-balance sheet SIVs was written down as investors fled from subprime mortgage related assets.
Many investors were caught off guard by the losses because little is publicly known about the specifics of SIVs, including such basics as what assets are held and what regulations determine their actions. SIVs essentially allow their managing financial institutions to employ leverage in a way that the parent company would be unable to due to capital requirement regulations.