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.
I would start by showing them my bank's online account.
They need to see the incoming amount and the expenses recorded online.
They need to understand that money does not grow on trees or magically appear so they can buy the latest gadgets.
Teenagers are very internet savvy these days - you would be surprised when you realize how fast they can get the concepts.
Tell them a brief history of bitcoins. The benefits.. the ease of use and the potential since it is a deregulated currency.
Be straight up, don't tell them a lot of stuffs. The teenagers are more interested in making money rather than knowing other stuffs that is not really necessary to know. It is better if you will just tell them the way to make a lot of money in bitcoin and through their journey it will be just automatic for them to know the other stuff like the essence of bitcoin and so on.