As explained above, the differences can be broken down into three small factors -
Clustered index modifies the way records are stored in a database based on the indexed column. Non-clustered index creates a separate entity within the table which references the original table.
Clustered index is used for easy and speedy retrieval of data from the database, whereas, fetching records from the non-clustered index is relatively slower.
In SQL, a table can have a single clustered index whereas it can have multiple non-clustered indexes.