Have you ever noticed the padlock symbol in your web browser’s address bar? Most websites, including the one you’re reading this article on, use SSL certificates to establish a secure connection. The padlock icon offers a visual indication that the website has a valid SSL certificate installed. It also signals that any information you enter on the website is fully encrypted in transit. In other words, nobody can eavesdrop on your connection and steal sensitive data like your password or credit card details.

But what exactly are SSL certificates, how do they work, and can anyone get one? Here’s everything you need to know.