With my limited knowledge of it in the context of addresses... Trillium is a data quality software tool that determines the validity and accuracy of an address as compared to the United States Postal Service database.

Works similar to: (try entering an address incorrectly)
http://zip4.usps.com/zip4/welcome.jsp

Helps companies keep their customer and vendor address data clean and in compliance with USPS' standards. Companies then qualify for discounted shipping since it's less likely to be "returned to sender".

Read the full version here:
http://www.trilliumsoft.com