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 think we should give a lot more credit to the upcoming generations in regards to what they understand about technology. It may be a lot easier to explain than you expect. This current generation grew up during a time of technology and I would use that to your advantage. Start off by relating to them with what they know about technology and go from there.. You can also use visuals like videos and graphics to help if necessary.