Views represent virtual pseudo tables defined by underlying queries, and they add another layer of abstraction to the system. Views hide implementation details and can present queries with complex joins and aggregation as a single table. Moreover, views can be used to restrict access to the data and provide just a subset of the rows and columns to the users.
There are two different kinds of views available in SQL Server: regular and indexed (materialized). Perhaps this is not the standard terminology; that is, regular views are just called views, although I will clearly differentiate them in the chapter.