What is technical SEO
Technical search engine optimisation (SEO) describes the efforts of a webmaster to ensure their website is compatible with search engine guidelines, and can be indexed and ranked for keyphrase searches accordingly.
What does this tool do?
Why should I care?
If the Google bot cant render your site or parts of it. It wont index as high. So you can run this tool on your website and give out to your web developer if he uses unsupported features.