Avast App Locker Is a universal app that will be necessary for all users. It serves one simple purpose, to block access to apps of your choice. That would be in the future to run this application you will need to enter a password. And those who do not know the password, simply will not be able to access this application. It is suitable as a caring parents that do not allow children to files and applications not for their age, and to people who just don't like when someone messes with them in the smartphone. And no one else can read your messages or correspondence.