An instant messaging application or client allows one to communicate with another person over a network in real time, in relative privacy. Popular, consumer-oriented clients include AOL Instant Messenger, Google speech, ICQ, Meebo, MSN Messenger, Pidgin (formerly maig), and Yahoo! Messenger. Instant messaging software designed for use in business includes IBM Lotus Sametime, XMPP and Microsoft Messenger.

One can add friends to a contact or buddy list by entering the person's email address or messenger ID. If the person is online, their name will typically be listed as available for chat. Clicking on their name will activate a chat window with space to write to the other person, as well as read their reply.