The [Rule Execution] tracing window appears when you click Execute rule and provides a wealth of information on the execution progress.
However, in case you accidentally closed it and want to review it:
On the Rules page, select the rule about which you need to view the execution details.
Click Open rule execution detail on the toolbar to open the window again.
Open rule execution detail allows you to check only the details of the last execution of a rule.
For more information on how to access the history records of all rule executions, see Monitoring rule executions