BitTorrent Sync FAQ *unofficial* - BitTorrent Sync - BitTorrent Forums:
What do the device icons mean?
Direct Connection - BitTorrent Sync is able to establish a direct connection to this device
In-direct (Relayed) Connection - BitTorrent Sync isn't able to establish a direct connection to this device, and therefore has connected via a intermediate relay server. It is preferable to have direct connections wherever possible, as this will generally provide faster transfer speeds over that of a relayed connection