Here are some of my thoughts:
- A digital library that stores information that cannot be changed (an immutable database)
- Open to anyone who wants to contribute (Permissionless)
- Resistant to hackers (Byzantine Fault Tolerant)
And maybe if I get deeper:
- A state machine where you can pay something to move from state A to state B, e.g. A vending machine. These state transitions are also called transactions.
- Each transactions are grouped and packed into a block. A block is an atomic unit of transitions that gets processed by nodes in the blockchain.