Often I'm asked to explain BTC to someone and occasionally I come up with something stellar that really nails it, but most times it's a rambling incoherent mess.
What I would like to see is a short and simple explanation of what BTC is that is suitable for someone non-technical to understand.
For me, I think the good way to explain bitcoin is to tell them that bitcoin in an online or modern investment. Whey they invest money, they will gain a profit higher that what can company give but they need to have patience in waiting.