"Blue Screen of Death" is the slang term for when a computer has a stop error. This occurs when a user is working and the screen suddenly turns blue and displays a variety of text and an error message. It's not always bad. For some reason the machine had an error that it couldn't work past and needs restart. On a healthy computer, this is very rare and, if you save your work often, not detrimental. A stop error is a big problem when it happens multiple times in a short amount of time.
If your computer encounters a stop error on any interval that can be considered more than very rarely, send helpdesk a ticket. Save all your files to your Home Directory. A technician will likely need to re-image your computer. For more information on re-imaging click here.