Your laptop probably came with an encryption software pre-installed and is configured to encrypt your hard disk, meaning that your data and files are getting saved on the hard disk in the encrypted state. To encrypt the data the software creates (usually randomly) an encryption key (a long string of characters and digits) and uses it as an input (kind of password) to the encryption algorithm. The algorithm scrambles the data in such way that it is vurtually unreadable without the key. It is then stores it on the disk. When your applications try to access the data, the software unsrambles the data by using the key and reversing it to the original state (otherwise, the applications would receive garbage data).
It is therefore, very important to backup the encryption key on a removable media, such as flash drive, because in case of the laptop failure you'll be able to mount your hard drive as a slave and recover data from it using any other encryption software and the the key. Without it you are out of luck. At work, we are required to use data encryption and using zecurion suite for storage and backup encryption
. It is actually pretty good with relatively low performance overhead. if interested, check them out and let me know how you made out.