Consolidated Quotation System

The Consolidated Quotation System (CQS) is the electronic service that provides quotation information for stock traded on the American Stock Exchange, New York Stock Exchange, and other regional stock exchanges in the United States and also includes issues traded by FINRA member firms in the third market. Nasdaq processes this data and provides it to its subscribers as the Composite Quotation Service.

Source: Wikipedia — Consolidated Quotation System (CC BY-SA 4.0)