doteveryone explains

Transmission security

The green padlock in a browser address bar that indicates secure data transfer

You might have noticed the green padlock symbol in your browser bar. It means that data is being transmitted securely from your computer to the website in question.

No computer that your data passes through on its journey can access what you're sending – it's private between your device and the endpoint.

(Our explainer ‘What happens when I upload a picture?’ tells you more about how data travels.)

The green padlock doesn’t mean that what you do on the website stays private, or that the end website stores your data securely.

All e-commerce websites should have the green padlock because they ask buyers to send credit card details. Never pay for anything on a website that doesn’t have a green padlock.

Other aspects of security:
Computers and devices