It sounds like you’re referring to the concept of a (also known as a virtual credit card number). This is a temporary, randomly generated number linked to your real credit card account, designed to be used for a single transaction or a limited time. It helps protect your actual credit card details from fraud, especially when shopping online with less trusted merchants.
This technology is a powerful weapon against data breaches, subscription traps, and card-not-present fraud. Major issuers like Capital One (Eno), Citi (Virtual Account Numbers), and privacy-focused services like Privacy.com have popularized the feature. For consumers, the ability to generate and discard credit card numbers on demand transforms online security from a passive hope into an active, manageable control. It allows you to shop on less familiar websites without fear, knowing that your real credit line remains safely hidden behind a one-time-use digital shield.
Here is an explanatory text on the topic: