I want to generate a lead performance report using the "Group leads by stage" and "Group leads by Email Address" options. What is the difference between the two fields and what will be the difference in the report generated?.
In lead performance reports, you will get groups with for each group the number of leads in this group.
Group by stage means that the "lead stage" will be used to group leads, while group by email will group them by email address (meaning will have 1 report line for each email address).
Give it a try, it will cause no harm and the result will be self-explanatory.