Also referred to as a ScreenTip, basically it is a message that appears when a cursor is positioned over an icon, image, hyperlink, or other element in a graphical user interface.
You can show a message on TOP POSITIONThis is a top position tooltip!, LEFT POSITIONThis is a left position tooltip!, RIGHT POSITIONThis is a right position tooltip! and BOTTOM POSITIONThis is a bottom position tooltip! using tooltip.
The tooltip is not just limited with just plain words, you can also put IMAGES on your tooltips.
Did you know that the tooltip came from older Microsoft applications like Microsoft Word? This had a toolbar where moving the mouse over the buttons displayed these tooltips.
Tooltips are great and the good thing is they can be easily done using CSS3 alone.