Advanced Segments are filters designed to alter all of the data displayed in Google Analytics. These segments could range from basic — only showing paid search traffic or filtering to sessions that included transactions, for example — to complex.
While Advanced Segments cannot be created in Raven, newly created segments will automatically import into Raven within 24-hours after they've been created. New segments can be created using Google's Segment Builder.
Keep in mind that segments are tied to the users that create them — not the websites themselves. When creating a new segment for use in Raven, be sure that you're signed into the account that was authorized in Raven.