Encryption stores all your phone and tablet’s data in an unreadable format. Once you power on your phone, you’ll need to enter the encryption PIN or password the same as your phone’s lock-screen PIN or password. This PIN or password decrypts your data to make it understandable. Without this PIN or password no one will be able to access your data. Android has an inbuilt encryption feature that encrypts all data. You can access it by entering a valid PIN or password each time you turn on your phone. source