If something is listed, it's included in a record or catalog. If you have a listed phone number, that means it can be found in a telephone book or in an online directory.
Anything included on a list of some kind is listed. When Wall Street traders talk about listed stocks, they mean shares that are on the official list of stocks traded on a stock exchange. When Realtors mention listed properties, they're talking about houses, buildings, or land on the official list of real estate that's up for sale. And when something is listed in a directory, whether it's a phone number or email address, it's on another kind of official list.