You can create maximum 249 non clustured indexes in a table and only one clustured index.
Example of Non Clustured index is : Book index in back side of each book, which contain a word and page numbers where you get those words. Basically It contain reference of each record as page number, and while user execute a sql query, it first checks while there is an index in that column or not. If there is a non clustured index so, it must contain all references of rows with matched data, and it points to those rows only. Otherwise it should search all record one by one and select only matched rows.
Example of Clustured Index : A Telephone Directory. A phone directorystill sorts entries into alphabetical order. The difference is, once we find a name in a phone book, we have immediate access to the rest of the data for the name, such as the phone number and address.
For a clustered index, the database will sort the table's records according to the column (or columns) specified by the index. A clustered index contains all of the data for a table in the index, sorted by the index key, just like a phone book is sorted by name and contains all of the information for the person inline. We can only create one clustered index on each table.
