FileVault 2 is the data encryption tool built in to the Mac operating system, OS X. It allows you to encrypt all of the files on your hard drive (including Documents, Pictures, Desktop, etc.) and then seamlessly access them at login. The result is you are able to work with all your files as normal when you are logged in. No one else can read your files, unless they login as you. This is important should your computer be lost or stolen, any confidential data on the hard drive would not be accessible by anyone without your user ID and password.
It is important to keep in mind that FileVault 2 uses your login password and a master encryption key to
allow access to your encrypted data. If you forget your password and lose
your encryption key you will no longer be able to access the data. The Office of Information Technology will assist you with backing up your encryption key to a secure network location.