She just said she does not understand Bitcoin on Twitter and asked people to explain. And got lots of answers in a short time.
I don’t understand Bitcoin either. At least not at the expert level some people who are concentrating full time on it.
But that does not matter much.
The unique thing about Bitcoin is that you need to trust no one to use it.
The common thing about Bitcoin is that you don’t need to understand it to use it. Do you understand how the CPU in your personal computer works? Do you use a computer?
So Rowling could go ahead and buy some bitcoins right now. On the other hand, she is not necessarily the target audience for the project. Someone in her position is well served by the traditional financial system, or any financial system for that matter.
Bitcoin shines when the alternatives are of dubious value. That’s why search interest for Bitcoin beats interest for Harry Potter in Venezuela right now.
And it beat Harry Potter by a factor of about five for a month in late 2017 in worldwide search interest. And it may well get there again.
But to answer to the request of “explaining Bitcoin” briefly:
It is the native currency of the Internet. Trustless, P2P and international. Any civilization that like humans has distributed computing like the Internet will obviously adopt a blockchain currency.