Each public private key pair can be thought of as a single note as shown below
- In order for that note to be good it has to be loaded up first. This is done by sending the public key to the person who will give you BitCoin
- Once loaded up you can now spend the BitCoin by using the private key.
The private key must be kept secret. If a person was able to get your private key they could then spend it. ( I think. Will need to verify this is complete and accurate description of behavior ). Certainly if another person had both the public and private key they would be able to spend.
QUESTION: How is the amount associated with the Public / Private key encoded?