Android's new "Running Apps" list is handy, but it's hard to tell exactly what happens when you swipe an app to remove it from this list. Does it kill the app? Does it kill background services? Android developer Dianne Hackborn explains.
In short, it quits the app in the same way pressing back over and over again does. Sometimes, that kills its background processes as well, but sometimes it doesn't:
...Removing an entry in recent tasks will kill any background processes that exist for the process. It won't directly causes services to stop, however there is an API for them to find out the task was removed to decide if they want this to mean they should stop. This is so that removing, say, the recent task of an e-mail app won't cause it to stop checking for e-mail.
If you really want to completely stop an app, you can long press on recent tasks to go to app info, and hit force stop there. Force stop is a complete kill of the app — all processes are killed, all services stopped, all notifications removed, all alarms removed, etc. The app is not allowed to launch again until explicitly requested.
So, basically, it's up for the app to decide, and it depends on how the app was coded. It's worth watching the screen in Settings > Apps > Running to see how each app acts — and whether you can swipe it away to save battery or whether you need to tweak its settings (or uninstall it altogether). We don't really recommend using that "Force Stop" button, for the same reason we don't recommend using task killers.