Learn in the textbookGUI Screen Controls, Menus, and Auxiliary Displays
DefinitionA tooltip (ツールチップ) is a short note that appears next to a button or icon when you rest the mouse pointer on it.
ExplanationPlacing the pointer over a control and holding it still without clicking is called hovering (ホバー), and a tooltip appears in response to a hover. When an icon's picture alone does not make its role clear, it lets you check what the control does before pressing it. Moving the pointer away makes the note disappear.
AnalogyIt is like a small name tag on each tool in a toolbox. You know what a tool is for before you even pick it up.
Memory hookRead it as tool plus tip, a small hint, and you get a quiet word attached to a tool.