This is a web page that makes a checklist out of the link that you follow to get here.
Not exactly: you can't edit the checklist, so it's not a great fit for tracking things. It's better for things like packing lists, maintenance lists, or other lists that you'll write once and go through repeatedly.
You probably followed a link that didn't have a checklist in it. You can make a new one by clicking on the "New" button up there. Go ahead, try it!
When you load this page, it runs some code that looks at the web address. It also saves the items you check off so that you can reload the page without clearing the list. You can read the source code here if you want to.
He's a fellow from Vancouver. He made this website.