I try to explain it in a concept of what they already understand. So i go for a bank transfer, apart from i explain what makes it different and better i.e. Faster, safer, cheaper. Once they get that concept I explain what a wallet is and then blockchain technology.
I think to get people interested is to mention something they already have a grasp of and then interest them with why it's better.
RE: How you explain what is cryptocurrencies to your parents?