Greenify is an app manager tool that lets you "Greenify" an app and is unlike the "Hibernation" tool featured by many other apps. A Greenify-ed app is in a state of hibernation state and unable to access system resources, bandwidth, or run background processes. However, Greenify allows you to run an app normally in the foreground when explicitly called by the user without any extra fuss. Just don't greenify your alarm clock or messenger!