Card sounds may differ from in-game as they get updated.
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.
Stun - Exhaust a unit. It can't attack or block next turn.
Contract - You may pay the number in additional power to get its bonus. If you don’t have enough power to pay some or all of the Contract, the remaining balance is applied as “debt” that is paid at the start of the next turn.
Debt - Your available power is spent to pay off Debt. If you can't pay it all, you pay at the start of your next turn.