I wouldn't tell much but will use simple words such as its a digital currency that can be use as payment for goods and services online whereas the seller is willing to receive bitcoin.
It has an unstable value that the market gives depending on the demand and supply of it. And if that isn't enough its better for him/her to watch tutorials that's explanation bitcoin with some visual graphics.
Definitely visuals! Infographics and other videos that covers the gist of crypto is good to start with
Video is a means of delivering information that's good and easily understood by them, rather than having to talk a lot but the results are always zero. Because not a few of them it's hard to catch what we are talking about.