"Security" means a financial asset that holds financial value and can also be traded depending on the security in question. Now with that said, a "security instrument" is a legal document that is used as a form of protection or assurance thereby providing evidence of property pledged to a lender as security for the repayment of the loan.
In real estate, a good example of a security instrument is a mortgage or deed of trust. The most important thing to remember in terms of security instruments as far as real estate is concerned is that these security instruments give a creditor the right to claim the property in order to recover debts.
