This is the Protect Files application icon, double click it to create your first encrypted space. Creating an encrypted space it’s very easy, just follow the online step by step guide which asks you the name you want to give to encrypted space, the size and the password you want to use to protect your data. You have to use the Protect Files application just to create new encrypted space files then you can close it.
Encrypted Space Files
These are the two types of files that you can create with Protect Files. The first one is a standard encrypted file, the second one is a self mounting encrypted file (it depends on what you chose to create in the preferences of Protect Files).
These files contain all your encrypted data, you can keep them on the Mac’s hard disk, an external disk, or a USB drive. When you want to access your files, simply double-click them, enter your password and the space will show up as a volume on your desktop.
The files are locked by default to prevent them from being moved to the trash and deleted accidentally. To remove the block, select the file in the Finder and uncheck the "Locked" check box.
Encrypted Space Disks
This is the Encrypted Space Volume (the icon can be white or gray), it contains all your protected files, documents and folders. You use it as a regular external disk: just copy the files you want to protect inside a volume. After working with it, eject the volume by clicking the Eject button in the sidebar of a Finder window or dragging its icons over the Trash.