PageSpeed Insights is a tool to analyze your website for possible errors and Troubleshooting tips. Also the online service checks the loading speed of the project and advises you on how to improve and what to remove.
With this service you can always know which components and scripts in your project load hosting and what you need to do in order to rectify this situation. Here scripts and styles and other elements are HTML documents.

PageSpeed Insights – check site for errors and loading speed

You are given the basic tools for the analysis and links to the scripts and the HTML code pages of your site that Google need to improve, compress, correct.
It should be noted that there is a review (test of agility) mobile version of the site, of course, if it exists at all on your project.
There are 3 types of symbol: red exclamation mark, orange exclamation mark and a green check mark.
They provide an excellent vision of the overall picture: the red color means that we need to fix in the near future, orange – after the first paragraph and the green indicator light is okay.