Use for rich interactive content anchored to a trigger. mini forms, detail previews, color pickers. Popovers are interactive (clickable content inside); tooltips are not.
When not to use
For simple text hints, use Tooltip instead
For action lists, use Menu instead
For complex forms, use Dialog or Drawer instead
Guidelines
Position aware: Popover should flip to stay in viewport.
Dismissable: Click outside or press Escape to close.
Keep focused: One purpose per popover. don't overload with content.