I deal with a lot of older people that know they need a blog/website, but know next to nothing (but usually more than they realize). So I've come up (over the years) with numerous alternative 'mix and match' analogies.

I often start by referring to any new WP site as comprising three building blocks. There is a 'skeleton' that does all the hard work. Then there is the 'skin' - a decoration that can be as simple or complicated as the user needs, with or without make-up. Then there is the 'brain' where all those wonderful musings and thoughts gets stored. If they want the site to 'do' something, then I segue to the 'app in your phone' concept.

Two analogies for us also come to mind: "not seeing the wood for the trees" and "the best teachers are usually the ones that have struggled to learn their subject".

Trying to explain it all in thirty seconds isn't going to work - it needs a game-plan that builds incrementally on previous experience. It's a process that slowly builds up confidence (I would never just install WP for them and leave them to it - "you'll work it out!", "you just need to do this, this and this!"). And one size just doesn't fit all - different analogies are needed for different people.