Coin age is a unit of measurement often used by proof-of-stake networks to calculate the value of a node's holdings during a hashing period. It can also be used to help determine transaction legitimacy, as older coins are less likely to be part of orphaned or fraudulent transactions.
Coin age is typically measured as: [number of coins] x [length of holding]. Examples: 1. If you had 1 coin and held it for 8 hours, you would have a coin age of 8 hours. 2. If you had 10 coins and held them for 4 hours, the coin age would be 40 hours.