The AdventureWorks and AdventureWorksDW are two sample databases introduced in SQL Server 2005. The AdventureWorks database is an online transaction processing (OLTP) sample database while the AdventureWorksDW is a data warehousing sample database. AdventureWorks and AdventureWorksDW have replaced the pubs and Northwind databases of earlier versions of SQL Server.
Both of these sample databases can be installed from client tools during installation as shown. Or you may download these separately from here and install/attach.