In Haruki Murakami’s dystopian novel 1Q84, a young and promising fiction writer Tengo Kawana ghostwrites a story that features, at some point, a sky with two moons. While describing it, the author does it with only a few words. When his editor Komatsu reads it, he urges Tengo to re-write it with the description expanded.
“Think of it this way, Tengo. Your readers have seen the sky with one moon in it any number of times, right? But I doubt they’ve seen a sky with two moons in it side by side. When you introduce things that most readers have never seen before into a piece of fiction, you have to describe them with as much precision and in as much detail as possible.” – Haruki Murakami. 1Q84
The same goes when you are presenting. When you introduce a new concept or a situation, something your audience have never seen / never experienced before, you must describe it with as much precision as possible.
If you want to save yourself the trouble of extensive descriptions – include in your presentation things your audience is very familiar with. Or even, what they’re seeing at the very moment when you’re presenting.
Such as yourself.
(It always works when I do it.)