This is a repository showing a web site with accessibility problems and possible fixes for them. It is used in a video class on Skillshare.
You can take the Product Management: Tools for Improving Product Accessibility if you want to, or use this repository for your own training needs.
The page with errors example is the one shown the class and features a few issues to find out using automated accessibility tools and developer tools built into the browser.
If you want to read up what the problems are without finding out yourself, you can check the error explanation page.
The fixed page example has most of the problems fixed and is a good resource to look at as an inspiration how to create your own solutions for the problems.