This is a fundamental security standard which ensures that your user’s connection cannot be tapped or manipulated.
HTTPS (Hypertext Transfer Protocol Secure) is an encrypted version of HTTP that uses Transport Layer Security (TLS) or the now insecure Secure Sockets Layer (SSL). HTTPS is a protocol on the Internet that is most often used in connection with services where only the sender and receiver must know the message, for example online banking.
It is your hosting provider (registrar) who can help set up HTTPS on your domain.
Read more about HTTPS at sikkerpånettet.dk, and test how secure your domain is.