A Popover is a dialog that appears on top of the current page. It can be used for anything, but generally it is used for overflow actions that don't fit in the navigation bar.
More contents:
Axure RP 10 downloads:
Axure Libraries: /collections/libraries
Axure Templates: /collections/templates
Product & UX Tools: /collections/ux
Free Products: /collections/free
Mobile Products: /collections/mobile
Axure Couse: /products/axure-rp-10-and-ux-core-skills-course