在ActionBar后退按钮，实际上是一个向上按钮，它应该带你到你的应用程序的导航层次更高的水平。后退按钮需要你，你看最后的地方。

The ActionBar "back" button is actually an "Up" button and it should take you to higher level on your app's navigation hierarchy. The back button takes you to the last place you were looking at.

另一个伟大的提示，以更好地undertand这是向上按钮应始终把您在您的应用程序的地方，而后退按钮可能会带你到另一个应用程序。

Another great tip to better undertand this is that the "Up" button should always take you to a place on your app, while the back button might take you to another app.

您可能需要阅读这篇文章，以更好地理解上的差异：的http：//开发商.android.com /设计/模式/ navigation.html

You might want to read this article to better understand the difference: http://developer.android.com/design/patterns/navigation.html