Clicking the camera button takes a screenshot of the entire map the player's character is currently in. The default zoom is 25% of original size, but can be changed via plus/minus buttons to 50%, 75%, or 100%. The default save location is:
You can also use this feature with the chat command <samp>/mapscreenshot</samp>. The command will let you specify filename and percentage as well, for example <samp>/mapscreenshot image01 100</samp>.