The action button is a UI element introduced by Apple in iOS as a way of representing doing something with the current page or piece of content with some other application. It has expanded in meaning to be a catchall for any secondary menu items or a method for simplifying the primary set of actions / buttons on a page or piece of content.
- - up through iOS6
- ... need button for iOS7-8
The action button is often used to mean "share", which is also represented quite differently on other systems:
The iOS7+ action button looks too much like "upload":
Blog posts and articles about the action button.
- 2014-01-27 Erin Jo Richey: UI Icons that Drive Me Crazy / The Action Button