The update, which appears in Software Update, is recommended "for all users and improves the security of Mac OS X." The previous 2008-001 Security Update is incorporated into this update and a restart is required.
Apple's knowledge base article #307562 has more information on 30 areas of OS X that are patched by Security Update 2008-002, including:
pax archive utility
Knowledge base article #61798 has more information on all Apple security updates.