Android Apps doesn't come with a "Quit/Close" button, as they are automatically managed by the OS. Indeed Android will close idle (opened) apps after a certain period of time, but doesn't it means that apps are still running in the background, consuming battery power, CPU and RAM resources..etc?
In this article you will learn two methods to close apps on Android devices:
From the multitasking view
The first method is to access background apps via multitasking view. The multitasking view is available on terminals equipped with Android 4.0 or later. Simply tap on the multitasking icon at the bottom left of the screen.
The list of current software will then appear.
To quit an application, simply drag it out of the list or perform a long press and choose " Application Information" > "Force Stop".
From the Settings menu
On the latest version of Android:
Go to Settings > More > Application manager.
Swipe to the left to view the current apps.
Select the app of your choice and tap on Stop.
On some phone models "Settings" then "Applications /Application Manager".
Click on " Manage Applications", select your application and click "Force Stop".