Imagine walling up every window and all but one door into your home. As long as you have the key, you're the only one who can get in. Encrypting your laptop does this, leaving only one door into your system—and your password is the key. Encryption protects your data even if your laptop is stolen and its hard drive removed. Apple, Windows and Android devices come with both encryption and backup functionality.
Of course, if you forget your password, you've got a serious problem. Start by making a complete backup of your data, then turn on encryption. If yours is a College-owned laptop, consult ITS before you encrypt!
For more tips on securing your devices and protecting your data, visit Safe Computing.