Creating a fixed Frame/box/something which has a transparent hole in between where content scrolls behind it. I want the front portion to be fixed and content scroll inside the box.

https://bennett-tea.com/tea-store.html (this is a perfect example) On the right there is a fixed frame in front like its a single section website and the content is changing inside the box. I find it quite challenging. Can someone please give me an idea on how to do it?