Full disk encryption (FDE) encrypts almost the entire hard drive of a device (or external storage media, such as USB flash drives), including the operating system and your data. This means that if your device is lost, stolen or seized, an adversary will not be able to gain access to your data by merely taking a copy of the storage. It is vital that you use a strong, unique password when enabling full disk encryption (and not the same password that you use to login to your device). However, be mindful that if you forget this password, you may lose access to your data. Also note that a strong FDE password will be undermined by a weak user account login password if this can also unlock the FDE key. The precise relationship between user account password and FDE decryption keys will depend on your device and operating system.