Another draft. I don't know where I was going with this one but it almost works on its own.
Separating style from content is pretty common in programming and web design. You have a file of 'content' that says
"I like turtles" and a separate 'style' file somewhere that says you want it purple, in size 20 Comic Sans. Or to take a slightly more complicated example you might have a draughts game where the board state is represented by some data structure – that's the 'content' bit – and then there's some 'style' code to display it prettily, render some nice pictures of squares and pieces and so on.
This so completely bog standard that it looks obvious, 'just the way things are', so it's worth pointing out that most of the world is not like that. Like if you have a 20 foot tall apple tree outside your house, there isn't a 'content' part that's a generic 20 foot tree, and then a 'style' part that you can swap out for a cherry tree if you get bored. You don't set the
hasLeaves property to
false in winter. You just get the whole lot in one big lump. The style is mixed in with the content, all at once. It takes a lot of engineering to produce something that's separated out like that.