The article is more of a how-to-use than how-it-works.

> Confidential assets and transactions on Liquid keep the amount and type of assets transferred visible only to participants in the transaction. Yet they still cryptographically guarantee that no more coins can be spent than are actually available.

I recently used Liquid to buy @TheVladCostea's magazine on https://raretoshi.com. The Aqua wallet I was using for iOS forced me to use confidential transactions to transfer to the site's wallet. I didn't have a reason for them to be confidential but fun to know they were sort of private. 