Some applications aren't ended completely when your mobile phone returns to the home screen. If you don't end them from the list of running applications, they keep running in the background which may slow down your mobile phone.
Step 1 of 3
End running applications
Tap the Application key.
Step 2 of 3
End running applications
To end one running application, slide your finger right on the required application.
Step 3 of 3
End running applications
To end all running applications, tap the end all applications icon.