You can filter out unwanted photos by using Ratings and Flags filters. This is useful when you want to only export / share few selective photos from a photoshoot. You can also use this to focus on particular segment of photos while culling.
Rating filter can filter photos equal to = / greater than or equal to >= / less than or equal to <= the specified rating. You can toggle between these modes using the given condition button >=. You can clear rating by selecting the selected rating again.
Flag filters are toggles for Picked / Unflagged / Rejected flags. Using these toggles you can include photos having / not having those flags.