Why do we type those two slashes in https://?

It turns out the double slash comes from an old 1980s computer system called Apollo Domain OS.

Back then, if you typed a single slash (/), your computer looked for files inside its own hard drive. The engineers at Apollo needed a way to tell the computer,

Hey, don't look inside yourself, look out at the network.

So, they decided two slashes (//) would mean "network."

When Tim Berners-Lee was building the World Wide Web, he just borrowed that exact rule.
➖ The colon (https:) meant this is the protocol, and
➖ The double slash (//) meant the web address is coming next.

The funny part is he later admitted it was a total mistake. The computer didn't actually need the slashes to understand the link. He joked that if he had just left them out, the world would have saved millions of hours of typing.

This comment answered it right. 👏