Repos are classified as a money-market instrument. They are usually used to raise short-term capital. The purchase of securities with the agreement to sell them at a higher price at a specific future date
For the party selling the security (and agreeing to repurchase it in the future) it is a repo; for the party on the other end of the transaction (buying the security and agreeing to sell in the future) it is a reverse repurchase agreement.
