The distance between the popover and the anchor element.
Live examples:
- [Combobox filtering](https://ariakit.org/examples/combobox-filtering)
- [Form with Select](https://ariakit.org/examples/form-select)
- [Hovercard with keyboard support](https://ariakit.org/examples/hovercard-disclosure)
- [MenuItemRadio](https://ariakit.org/examples/menu-item-radio)
- [Submenu](https://ariakit.org/examples/menu-nested)
- [Toolbar with Select](https://ariakit.org/examples/toolbar-select)