Disk encryption is one method you may use to enhance the physical security rating of your computer. From my experience, it is rarely used, which is a shame because it is one of the most effective safeguards against unauthorized physical access to data stored on a computer.
It can take the form of full disk, or per partition, and may be configured during or after installation. However, the most effective is full disk during installation. When disk encryption is enabled, you will be prompted for a passphrase which will be used to lock or encrypt the disk.

This article offers information on how to manage disk encryption passphrases and key slots.