What are Covering Indexes and Covered Queries in SQL Server?

Question

Can you explain the concepts of, and relationship between, Covering Indexes and Covered Queries in Microsoft's SQL Server?

Answer 1

A covering index is one which can satisfy all requested columns in a query without performing a further lookup into the clustered index.

There is no such thing as a covering query.

Have a look at this Simple-Talk article: Using Covering Indexes to Improve Query Performance.