Bitcoin is difficult to explain. I also felt difficulties in understanding bitcoin for the firs time. Let's share how to explain bitcoin to children of teenagers. In My country I can say 98% children don't know bitcoin. In fact, bitcoin can be future money. If the children not familiar with cryptocurrency or bitcoin, how can they face the digital era in the future.
Explaining bitcoin and altcoins to children is very easy. Just dont make the mistake of telling them about blockchain/transactions/fees etc.
Just like fiat is being digitalized, children will only know about money/bitcoin through apps. If you have a wallet on your phone, and it says there is 3 coins, then they know that they have 3 coins. It's as simple as that.
They dont need to know the mechanism behind it to understand it.