"Alternate universe" is an informal word that you can use to describe a world where the typical rules don't apply, or where things are radically different from how they really are.
Imagine you work at a shoe store and a customer tries to return a pair of shoes after she has worn them several times. She doesn't understand why the store won't take the shoes back. You might think to yourself, "This customer is living in an alternate universe." That means, you think the customer is living in a world where all the normal rules don't apply.
In today's lesson, we invited you to imagine an "alternate universe" where all the rules of traditional economics and banking don't exist. But then came the twist: this "alternate universe" is a description of cryptocurrencies.