“Alternative trading systems (ATS), is a US regulatory term for a non-exchange trading venue that matches buyers and sellers to find counterparties for transactions. An ATS must be approved by the United States Securities and Exchange Commission and is an alternative to a traditional stock exchange. The equivalent term under European legislation is a Multilateral Trading Facility (MTF).
These venues play an important role in public markets for allowing alternative means of accessing liquidity. They can be used for trading large blocks of shares away from the normal exchange, a practice that could otherwise skew the market price in a particular direction, depending on a security’s market capitalization and trading volume. ATSs are generally electronic but dont have to be, ATS can to be distinguished from electronic communication networks (ECNs), that are a “fully electronic subset of ATSs that automatically and anonymously match orders”. (source: Wikipedia)”
The Financial Services Commission decided to introduce ATS as a means to improve efficiency of the Korea Exchange and create a more investor-friendly trading environment. Securities firms will be allowed to set up ATSs from August 29, 2013.