A feature of Windows 95 that displays a line of descriptive text under an icon when you move the pointer over that particular icon

Small labels that appear when you rest the mouse cursor on a button or feature. You can turn these off or on in the User Options tab of the Settings Panel.

Tooltips are small windows displaying a help echo (q.v.) text that explains parts of the display, lists useful options available via mouse clicks, etc. See section P.18 Tooltips (or "Balloon Help").