Spotlight search to make intelligent use of metadata

Technical document
"Working With Spotlight," released by Apple to its developer site on Tuesday, reveals an unprecedented effort to transcend the limitations of the traditional,
hierarchical file system. The new Spotlight search technology, to be incorporated in the Tiger operating system, will be driven by The Spotlight Store, a system-level database that stores metadata about your files.

You will be able to build up complex queries in the Finder and get a list of files in response to those queries.
Queries can be saved for frequent use. Searchable file metadata is going to be the key to managing an ever-growing volume of information on your desktop.