Correlation sets on invoke activities, which deal with outbound operations, are used to validate that outgoing messages contain data which is consistent with the data contained within specified correlation set instances. The Correlations tab in the Invoke Property Editor dialog box enables you to examine or specify a correlation set.
The tab shows:
Names of correlation sets
The initiation of a correlator
The pattern associated with the correlation
For more information see Understanding Correlation. Using the Correlation Wizard.