Depository receipts
A depository receipt is a security that is offered as a "tracking stock" on another foreign market. For instance a Chinese company wishing to raise more money may issue a depository receipt on the New York Stock Exchange, as the amount of capital on the local exchanges is limited. These securities, known as ADRs (American Depositary Receipt) or GDRs (Global Depositary Receipt) depending on where they are issued, are typically considered "foreign" and therefore trade at a lower value when first released. However, they are exchangeable into the original security (known as fungibility) and actually have the same value. In this case there is a spread between the perceived value and real value, which can be extracted. Since the ADR is trading at a value lower than what it is worth, one can purchase the ADR and expect to make money as its value converges on the original. However there is a chance that the original stock will fall in value too, so by shorting it you can hedge that risk.