I don't think there's an "under the hood" to speak of. A Data Warehouse could be built out of RDBMSs or something else. I think it's mostly a buzzword, but if

I don't think there's an "under the hood" to speak of. A Data Warehouse could be built out of RDBMSs or something else. I think it's mostly a buzzword, but if I had to define it, I'd say that it's a data store which isn't directly involved in operating your product, rather, it's data that you gathered and stored outside of the product, to allow data geeks to run their analysis jobs without them needing to touch your production database.