The Page Speed Score indicates how much faster a page could be. A high score indicates little room for improvement, while a lower score indicates more room for improvement. The Page Speed Score does not measure the time it takes for a page to load.
What’s neat about PageSpeed is not only that it tells you that your webpage has room for improvement, but it also gives recommendations on how to actually make those improvements. The color coded analysis corresponds to the same color of the set of recommendations.
Another feature of PageSpeed worth mentioning is its ability to give a mobile analysis for your website. With this feature, you can find out your website’s loading score on mobile devices and (also) give recommendations for improvement. Page Speed Mobile analysis does not use real mobile devices. It only emulates a mobile device and fetches a site with a webkit renderer found on iPhone and Android devices.
This is a very useful tool for web developers, bloggers and first time website owners who are looking for ways to make their site(s) faster.