My coworker told me he was going to start a business selling clouds.

This joke tickles our funny bone with a clever twist on modern tech jargon. The setup immediately makes us think of "the cloud" in terms of computing – that vast, intangible network (Review) of servers and data that powers so much of our digital world. Companies like Amazon, Google, and Microsoft have built multi-billion dollar businesses selling "cloud" services, making it a very real and lucrative industry.

However, the punchline yanks us back to the literal meaning of clouds: those fluffy, watery masses floating in the sky. These are, of course, utterly impossible to bottle up and sell, being essentially just condensed air and water vapor. The humor comes from this sudden shift in perspective, playing on the double meaning of the word "cloud" and the absurdity of trying to monetize something that is freely available and physically uncontainable. It's a classic example of wordplay, subverting our expectations with a dose of literal-mindedness and a nod to the old idiom about "selling air" when a product has no substance.