The Clustered Index Seek logical and physical operator uses the seeking ability of indexes to retrieve rows from a clustered index.
The Argument column contains the name of the clustered index being used and the SEEK:() predicate. The storage engine uses the index to process only those rows that satisfy this SEEK:() predicate. It optionally can include a WHERE:() predicate, which the storage engine evaluates against all rows satisfying the SEEK:() predicate (it does not use indexes to do this).
If the Argument column contains the ORDERED clause, the query processor has determined that the rows must be returned in the order in which the clustered index has sorted them. If the ORDERED clause is not present, the storage engine searches the index in the optimal way (not guaranteeing the output to be sorted). Allowing the output to retain its ordering can be less efficient than producing nonsorted output.