AOL was an "online service", internet connectivity was provided starting in the mid-90s but the real value was in their proprietary members-only services. An online service was more or less a large BBS you dialed into via modem, the first of which could be accessed with an ordinary telecoms program but later ones like AOL and Prodigy required special client software that could decode the proprietary protocol allowing the service to send graphics, menus, and other information to present a UI to the user.