the ctooltipctrl class encapsulates the functionality of a “tool tip control,” a small pop-up window that displays a single line of text describing the purpose of a tool in an application. a “tool” is either a window, such as a child window or control, or an application-defined rectangular area within a window's client area. a tool tip is hidden most of the time, appearing only when the user puts the cursor on a tool and leaves it there for approximately one-half second. the tool tip appears near the cursor and disappears when the user clicks a mouse button or moves the cursor off the tool.