When explaining bitcoins advantages over cash to someone else, there are a few things that come to mind:
1. They cannot be counterfeited
2. Can be sent anywhere in the world with no (or very very low) fees
3. Mining fees dont go to big banks
4. Low transaction fees, coinbase estimated bitcoin could reduce payment processing fees worldwide from $500 billion to $50 billion, so 1/10th of current level
Any other to add to the list?
It works almost like email but for money with some amazing qualities such as: limited supply, irreversible, non-freezable, non-counterfeitable, pseudononymous and almost free to use.
It's basically the equivalent of digital cash or gold that you can almost instantly send to anyone, anywhere in the world at any time.
These two sentences I'd wager would be the best when dealing with a lay person.