Cluster Index:

• A cluster index creates on primary key.
• A cluster index create automatically when primary created on the table.
• There can be only one cluster index per table.
• A cluster index sort and store data in a table based on columns included in index.
• A cluster index takes space of table.

Non-Cluster Index:

• There can be multiple non cluster index per table.
• Non clustered indexes store both a value and a pointer to the actual row that holds that value.
• A non cluster index takes space on the server.