Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online.A security is a fungible, negotiable instrument representing financial value. Securities are broadly categorized into debt securities (such as banknotes, bonds and debentures); equity securities, e.g., common stocks; and derivative contracts, such as forwards, futures, options and swaps. The company or other entity issuing the security is called the issuer. A country''s regulatory structure determines what qualifies as a security. For example, private investment pools may have some features of securities, but they may not be registered or regulated as such if they meet various restrictions.