Difference between clustered and non-clustered index

I am explaining you with an example, The Telephone 
Directory is a fine example of Clustered Index as data and 
index are at the same page, whereas index in the back side 
of the book is a fine example of non-clustered index and 
non-clustered index is a fast B-tree structure as index 
just points to the data page. Also only one clustered index 
is possible per table and 249 non-clustered index per table.

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