Open Banking gives the power back to you, the customer. Instead of the banks themselves, you will own your banking data, giving you the power to share it with licensed third parties, such as other banks, products, and services. Open Banking means that providers that are regulated by the Financial Conduct Authority, such as Lumio, can sync your accounts using secure connections called "Application Programme Interfaces" or "APIs".
It's a bit like when you sign in to another app via Facebook or Google, it doesn't change or allow unlimited access to your actual account, and you can stop access at any time from your banking app. You'll get prompted every 3 months to reconnect, so you can never accidentally leave the connection running.