The easiest way to explain and teach about bitcoin is to give a simple but efficient introduction on its history. It's very important to establish the interest first and let the person know that Bitcoin is something of value and can be converted into money.
Well I think it depends on whose you're gonna teach. With the young adults nowadays, the fact that they are very techie and is very much exposed on the internet and social media, they are more likely to learn fast. You just give them a brief overview of the basics, the things that will caught their interest and surely this will boost their eagerness to explore more about Bitcoin.