AT&T Inc. is a multinational conglomerate holding company. Tracing its origins to 1877, AT&T is engaged in telecommunications, it operates mobile and fixed telephone services in the United States through AT&T Communications. It is also the parent company of mass media conglomerate WarnerMedia, one of the world’s largest media and entertainment companies.
The market capitalization of a company, more simply referred to as "market cap", is the total market value of a publicly traded company's outstanding shares. It is often considered as a key indicator of what a company is worth.