US Stocks are typically only listed on one exchange, generally NYSE or NASDAQ. There have been some in the past that were listed on both exchanges, but seems like that isn't something companies do anymore.
I am trying to learn more about exchanges and markets and was looking in depth at the mechanics behind IEX; what is the difference between being listed on an exchange and simply trading on an exchange?
For example, IEX was approved to become a listing exchange, but their only "listed" company IBKR left recently to go back to the NASDAQ and IEX has since shuttered their corporate listings product line.
IBKR could trade on the IEX before, during, and after it was "listed" on the IEX, so I'm really not sure what the difference or significance today is regarding being officially listed on an exchange and simply trading is? I know that each exchange has its own rules and regulations to being listed with it, but other than that (ex NYSE has more stringent requirements), is there any significance? There's nothing that limits what exchanges a US stock can trade on in the US (provided it is registered with the SEC).