We are working on our first data warehouse project and following this same learning curve, here is what we've learned about the differences:

Your ODS takes the form of a typical normalized schema, the type we are used to with transactional systems.

The DW on the other hand is used to translate the data from the highly normalized ODS schema into the star/snowflake schema(s) that are typically used with DW analytics.  In the DW you design fact tables that store the data elements to be reported on and associate those fact table with various dimension tables that provide a hierarchy of how you will view the fact tables -for instance time: day/week/month/quarter/year is typically a dimension.

In short, the DW is just another way to organized your DB in order to make it friendly for analytics.  Hope that helps.