What is the average number of stars assigned to The simpson 20s: S20-E12? What is the said episode all about?
average number of stars refers to AVG(stars); simpson 20s: S20-E12 refers to episode_id = 'S20-E12'; episode all about refers to summary
SELECT AVG(T2.stars), T1.summary FROM Episode AS T1 INNER JOIN Vote AS T2 ON T2.episode_id = T1.episode_id WHERE T1.episode_id = 'S20-E12';