Facebook chat enables you to communicate with friends in real time. The chat sidebar, which appears in the right column of any of your Facebook pages, lets you know who's available to chat. Members' names are displayed with symbols, which are continuously updated to show availability.
The green dot that appears beside a friend's name in your Chat menu signifies his ability to chat with you. He is logged on, using Facebook from his computer, and has chosen to display an available status. Messages you send will appear in a small pop-up dialog box in his Facebook page. He can respond instantly if he so chooses.
The blue mobile phone-shaped icon that appears beside a friend's name in your Chat window implies that she's currently available to chat with you. She's using one of the Facebook Mobile apps from her smartphone, or other mobile device. Messages you send will appear on her Facebook Mobile app pages, as on-site notifications, or as text or email notifications. Friends who choose to do so may respond instantly.
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