To view or edit a correlation key's properties, double-click its Browser or list entry. The property sheet tabs and fields listed here are those available by default, before any customization of the interface by you or an administrator.
This tab lists the variables (see Variables (BPM)) that define the current correlation key.
You can add variables to a correlation key to gather variables that are related to the same communication. The correlation key can then be associated with a process implemented by an operation.