Spotlight's index of your hard drive includes information on practically every file on the drive, but since it is geared toward relevant search results, by default Spotlight does not include options to show system files however, Apple does include a number of hidden filters that you can use to enable these results in your searches.
While this feature's primary use is for locating user data and resources you may use, such as Applications and system preferences, it can also be used to find practically any file on the system.
The Spotlight feature in OS X is a convenient tool for locating your files, contacts, e-mails, and other information by searching through an index of file content and metadata in addition to file names.
