Instant Exchange allows you to send bitcoin and pay for it with your local currency from the same page. You can also receive bitcoin and Coinbase will execute an instant sell in the background. The sell will credit funds to your local currency wallet.
Instant Exchange is a great tool for people who want to use bitcoin but prefer to cash out immediately to fiat currency. The fiat currency value of each conversion transaction, after Coinbase’s conversion fee, will be reflected in your USD, EUR, and/or GBP wallets. Instant Exchange is supported only for users who hold fiat currency wallets with Coinbase.
For more info, please follow this link:
https://support.coinbase.com/custome...stant-exchange