On Emercury you have two ways to build a segment. One is using lists as the source of your segment. The other is using reports as the source of your segment. We've covered the first method in this document and we even show you some quite advanced ways of fine-tuning such segments using condition groups.
However, what a lot of people don't get is that building segments off of reports provides you some super-advanced possibilities, in a very simple way. In fact, when people first discover what they can achieve by building segments off of reports, they are usually blown away.
When should I build segments off of reports and not lists?
The best way to illustrate is to just look at an engagement metric like "opened" or "clicked". If you go to build a segment off of lists, when you choose the "opened" condition, you are telling the segment to match all subscribers in the chosen lists who have opened any of your emails. You can filter that down by time-range, but not by specific emails.
What if you only care whether people opened certain specific emails? Well, that's where building segments off of reports comes into play.
In that case, you want to go the new segment option and choose "off of report", then choose the report(s) about the email(s) you care about. You can then choose "opened" as your segment-building condition, and it will populate the segment with all the people who have opened those specific emails.
This will be irrespective of when they opened them, or what list these subscribers belong to. This is perfect if you don't even know what lists you sent a given email to. You just care who opened the email. Same with the timeframe. If you don't know or care in what timeframe a person opened emails, but are more concerned with the specific emails opened, the "report-based segment builder" is right for you.