ISIN stands for International Securities Identification Numbering system and is a 12-digit alphanumeric code that uniquely identifies a specific security, such as a stock or bond. The ISIN code is the only common securities identification number that is universally recognized. It is used for numerous reasons, including clearing and settlement, and ensures a consistent format so that holdings of institutional investors can be tracked consistently across markets worldwide. The ISIN and its associated metadata identify aspects of an instrument such as the name of the issuer, the issue description, and terms such as currency, nominal value, and maturity, to name a few.

ISINs are administered by a National Numbering Agency (NNA) in each country that currently uses the system. The first two letters of an ISIN code identify the companys nationality, followed by nine alphanumeric characters that identify the security, and the last digit acts as a check digit to prevent errors and ensure authenticity of the code.

The purpose of the ISIN is to provide a universally applicable identification number for international securities and derivatives with the goal of reducing delay, mismatches, and confusion in global financial markets. It has brought greater efficiency and transparency to the global financial system, facilitating international trading and helping to prevent errors and fraud. ISINs allow investors to easily and accurately identify and track the securities they own, as well as enable market participants to process trades and settle transactions efficiently.

In summary, ISIN is a unique identifier assigned to a specific security, such as a stock or bond, and is used to facilitate trading and settlement processes. It is administered by a National Numbering Agency in each country that currently uses the system and consists of a 12-character alphanumeric code that uniquely identifies a security. The purpose of the ISIN is to provide a standard and unique identifier that enables efficient tracking, settlement, and clearing of securities transactions.