Live sessions are video chat gaming sessions, run over Google+ Hangouts, that involve the players working to accomplish a certain set of goals with more coordination than is possible in downtime.
These sessions will take place at the end of the month, touching all the items in step four of the Monthly Turn in the Downtime section, and serve to tackle certain large problems directly or as a group rather than individually or through NPC proxies. Usually this will mean engaging in exploration, handling especially tough combat, making political maneuvers, or dealing with particularly nasty conspiracies.
Each live session should take between 1.5 to 4 hours of play, depending on how much there is to do and how the individual players feel.
Attendance is not mandatory, but the group will work best when it gets an opportunity to handle things like this and experience gained from encounters during live sessions can be quite helpful.