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.
To give a brief background of bitcoin is easy because all they have to know and all we have to explain is what is the definition of bitcoin and how it works. I would probably use compatison in order for kids to understand it more, but when it comes to teenagers, I would explain it as it is because it would be comprehensive. Although, explaining some bitcoin activities would be quite difficult.