I have likely misquoted or even misconstrued some of Tori's points, so you can find her original slides on slideshare, and New Relic have lots of other information on Site Reliability Engineering here.
1 What should SREs do?
2 How should SREs help build reliability?
Tori started by referencing the Google SRE books, "Site Reliability Engineering" and "The Site Reliability Workbook" (I really need to get around to reading these!), but asking how the rest of us mere mortals who don't work at good deal with SRE.
Continuously improve reliability of your application, and ultimately to have a good user experience.
How should SREs help build reliability?
If so, review them – are they understandable to someone not familiar with the system, at 2am during an outage?