How Do You Instant Message People Who Do Not Have AOL?

You cannot instant message anyone with an AIM (that is an America Online Messenger) if they do not have the AIM Software. Instead if both of you have Google talk, or yahoo messenger or msn messenger facilities installed on your respective computers you can instant message with the help of those softwares.
Instant messaging or IM is a type of real communication between two or more users or people which is based on typed text. The text is conveyed through computers that are connected over a network, like the Internet for example.
Instant messaging applications first appeared in the 1970s on the multi-user operating systems like UNIX. Initially they were used to facilitate communication with other users that were logged on to the same machine, later to users on the local network, and finally across the internet. Some of these softwares used a friend-to-friend protocol (eg talk, ntalk and ytalk), and others required friends to connect to a server (see talkers and IRC). Because most of these protocols were basically inside a console window, many of those discovering the internet during the mid-1990s tended not to encounter these softwares.