Screaming Frog is a website crawler that allows you to quickly and easily analyze your website's structure and on-page elements. One of the key metrics that it tracks is the "indexability" of each page. This simply refers to whether or not a page can be found and indexed by search engine crawlers. If a page is non-indexable, it means that it might not be indexed by search engines and most likely not appear in any search results. There are a number of reasons why a page might be non-indexable, but the most common reason is that the page has been blocked by a no-index tag. In other words, the website owner has specifically told search engines not to crawl that particular page. Non-indexable pages can also sometimes be caused by technical issues, such as incorrect redirects or 404 errors. Regardless of the cause, pages that are non-indexable will not contribute to your website's SEO and should be fixed as soon as possible.