How do I close an application in Android?

Unlike many other Operating Systems, Android does by default not have a dedicated button to close an application manually. This is because Android is designed to manage the running applications itself and close them as needed.
SOLUTION
By design, Android handles the memory and time assigned to applications. This ensures that applications that are left opened do not cause the smartphone to slow down or run out of memory.
In exceptional cases, you may need to force close an application, for example when a program fails to respond. Use the following steps to force stop an application:

1. Open the Applications tab and tap Settings, and next tap Applications.
2. Tap Manage Applications. In the list of running applications, select the application you wish to close and tap Force Stop.

Alternatively, on the Android Market, utilities are available that help ending tasks and closing applications.
DID THIS FIX THE PROBLEM?
In case a forced stop to an application fails to resolve the problem you encounter, restart the smartphone.