Website that serves as a gateway or a main entry point ('cyber door') on the internet to a specific field-of-interest or an industry. A portal provides at least four essential services: (1) search engine(s), (2) email, (3) links to other related sites, and (4) personalized content. It may also provide facilities such as chat, members list, free downloads, etc. Portals such as AOL, MSN, Netcenter, and Yahoo, earn their revenue from membership fees and/or by selling advertising space on their webpages. Also called portal site or web portal.