The AMP cache checker checks whether a website is already indexed in the Google AMP cache and can therefore be displayed more quickly using the Google search.
Part of the loading time optimization for Google AMP pages consists of saving the Google search in the search engine cache. AMP pages are loaded directly from the faster Google server instead of the actual server of the website.
With the AMP cache checker you can check whether one of your URLs has already been included in the Google AMP cache or not.