The row of people focusing right now used to mix everyone together — friends you follow and strangers alike. It's split in two now. Home keeps the people you follow, so it stays quiet and familiar, and Explore has everyone else who's focusing at this moment.
Follow someone from Explore while they're mid-session and their card hops straight over to Home. Both rows stay live as people start and finish, and tapping any of them takes you to their profile.