Is information architecture and database referring to the same thing? What are the differences?
You can think of database development (data modeling, etc.) as a subset of information architecture. The former is simply modeling your data persistence for storing your data at rest. The latter, however, can include considerably more. Rich domain modeling, software interaction, documentation, etc. are all "information" being "architected" in an enterprise.
If all your enterprise needs to do is persist data to a database, then the two are roughly the same. But if your business objects interact in more meaningful ways than just relational data schemas, and if there's more information about your enterprise than those schemas, then the information architecture for your enterprise would (should) include much more than just the database.