There are two different types of indexes:
- Clustered indexes
- Nonclustered indexes
CREATE CLUSTERED INDEX Idx1 ON dbo.Employee (EmployeeID) GO
Nonclustered indexes do not alter the way in which the data rows are stored in a table.
Nonclustered indexes are created as separate objects from the database table and have pointers back to the data rows in the table.
CREATE NONCLUSTERED INDEX IX_ProductVendor_VendorID ON Purchasing.ProductVendor (BusinessEntityID);
More Information - https://docs.microsoft.com/en-us/sql/relational-databases/indexes/clustered-and-nonclustered-indexes-described?view=sql-server-ver15