When Android phones first hit the market, multitasking was one of the key differences between the Android phones and Apple's iPhone. While the iPhone could run only one application at a time, Android phones could run multiple applications in the background, so that when you returned to that app, it was right where you left it.
Since then, the iPhone OS has received upgrades that give it multitasking capabilities, but the old situation nicely illustrated one of the issues between single-tasking and multitasking operating systems. All those apps running in the background of the multitasking OS eat up available memory, slow your phone down, and drain the battery life. So the single-tasking setup is not without its virtues.
Advanced Task Killer Free gives you more control over how to manage your phone's resources. It will display the list of apps your phone is currently running. From there you select the apps you would like to "kill", that is, turn off. From the settings, you can also select whether or not the app will auto-start when your phone turns on, and whether to access Advanced Task Killer from the notification bar of your phone. You have an option to enable an "Auto Kill" feature that automatically kills apps, and you can set the level for how aggressively you want this feature to behave. You can also create 'ignore' lists for apps that you never want killed.
One thing I really appreciate about Advanced Task Killer Free is the help section in the menu, which does a good job of explaining all the app's features and answering frequently asked questions. All in all, this is an essential tool for anyone who wants to get the best performance out of their phone.