An equity-linked security (ELKS) is an innovative financial instrument used by companies to raise capital and to provide investors with an alternative investment option to traditional fixed-income investments. These security instruments are often structured as bonds, but their payment is linked to an underlying equity market benchmark such as a stock index.

ELKS offer investors the opportunity to earn higher yields than what traditional fixed income investments may yield. The payment structure of an ELKS is variable and depends on the underlying security's performance. For instance, an investor may purchase a bond whose payment is linked to the performance of the S&P 500. As the index rises, so does the payments to the investor. Similarly, if the index falls, the payment for the bond will also decrease.

However, the payment structure of ELKS does have one major risk associated with them. Since the payments are linked to the performance of an underlying security, there is no guarantee of a return on investment. If the underlying security performs poorly, it is possible that the investor may suffer a significant loss.

Another type of ELKS are market-linked securities. These are relatively new instruments and they are designed to perform similarly to a stock. A market-linked security is created from a pool of underlying assets, such as stocks, bonds, and commodities. These securities allow the investor to participate in the performance of the pool of assets without having to directly own any of the assets in the pool.

ELKS have become increasingly popular with both corporate and individual investors as a way of raising capital and providing alternative investments to traditional fixed-income options. For example, banks have begun offering ELKS to enable higher returns for customers without having to take on too much risk.

In summary, an ELKS is a type of debt instrument with variable payments linked to an equity market benchmark. They provide investors with the opportunity to earn higher yields than traditional fixed-income investments, although they also come with greater risk. Banks and other financial institutions are increasingly offering ELKS, as are market-linked securities which provide exposure to a pool of underlying assets.