Card sounds may differ from in-game as they get updated.
Endurance - Units with Endurance ready at the start of each players turn, so they can attack and still be ready to block during the enemy turn. Additionally, they are completely immune to enemy stun and exhaust effects.
Flying - Flying units can only be blocked by other flying units, but can block ground units normally. They can also be directly attacked by Killer units and Relic Weapons.