Coinbase Card is like a credit card that lets you spend crypto. More specifically, it is a Visa debit card, funded by your Coinbase balance. Right now Coinbase Card is limited to UK customers.
How it works is that, it will instantly convert crypto into fiat for a fee when you use the card.
Products like this aren’t exactly using crypto as a payment system, however they are a step toward adoption that allow people to use their crypto as if it was being used directly as payment.
This is very useful if your wealth is in crypto and you want to purchase goods at places that aren’t set up to take crypto (as it avoids having to cash out of crypto, deal with the tax implications, and then spend the money yourself, instead it is all done in one fell swoop via the Coinbase Card).
You can learn more on the official coinbase site: https://www.coinbase.com/card.
TIP: Converting crypto to fiat for using as money is a taxable event in many countries… so make sure to keep your records.