What does the term alias mean in the context of payment cards? I understand it's somehow linked to a card number but what is its purpose?
An alias usually refers to a disposable or one-time use credit card number. These are also called temporary or virtual credit card numbers. Some credit card companies will allow you to generate a credit card number that links to your main account but is different from your main account number. You can usually set the number to expire after a certain amount of time or to only accept charges from a specific vendor or up to a certain amount. This allows you to make credit card purchases without as much worry about fraud, because your original credit card information is still hidden from the merchant.
You may also hear about an alias on your credit report, which is simply a different name that's also listed on your credit report. This could occur because you changed your name (through marriage, for example), or someone a misspelling ended up on the report.