Facebook features a built-in instant messaging tool that supports text-based chat with any Facebook user in your Friends list. The interface -- which is located in the right sidebar of your Facebook page -- indicates your Friends' online status with a small icon displayed next to the user's name.

Icons

If you see a friend's name next to a lit green dot, it means that friend is actively using Facebook and is available for chat. Friends with a mobile phone icon next to their names can see your chats and messages on a smartphone. Friends that do not have an icon -- in other words, there is no lit green dot or mobile phone displayed -- are not currently on Facebook or available for chat. Messages sent to these friends will go directly to the user's private message inbox.

Turn Chat On and Off

If you prefer to browse Facebook privately, you can make yourself unavailable for instant messaging by turning Chat off. Click the gear icon at the bottom right of the chat window and select "Turn Off Chat" to disable the feature completely. If you prefer to leave chat available for only a select few friends, click the gear icon and select "Advanced Settings" instead, then select "Turn On Chat for Only Some Friends" and enter the names of friends for whom you'd like to allow chat.