what is the use of non clusters index in a table

From MSDN

Quote:

A nonclustered index is an index structure separate from the data stored in a table that reorders one or more selected columns

1. Nonclustered indexes can often help you find data more quickly than searching the underlying table
2. The nonclustered index can point the Database Engine to the rows in the underlying table
3. Nonclustered indexes are created to improve the performance of frequently used queries not covered by the clustered index or to locate rows in a table without a clustered index

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