Android Back Button Closes app?

Not sure if this by design. Open app on Android device. go to different pages. Clicking the home button seems to put the app in the pause state. If I select the app from recent or even click the app icon again and it will open the app with where it left off.

Open app up and click the back button I am taking back to home page. Click the App again I get a black or white screen (no splash screen) and the home page of my app is presented. Starting all over.

Is this correct behavior?