Speed Category

The overall speed of a website, as experienced by real users, is summarized into a single score. This score takes all of the Google PageSpeed measurements into account and averages the speed of the website across many user experiences. The result is one of three categories being assigned to the website: SLOW, MODERATE, FAST.

Obviously, websites should aim to be in the FAST category and they can achieve this by optimizing their webpage to load faster. The best way to do this is to reduce the size of images, CSS and Javascript and making sure everything loads fast. After making some improvements to a website, there will be some lag before this metric improves. This is because the score is averaged over the course of several days or weeks, so it will take time for the old data to fall out of the back of this window.

For more information, please read the documentation on Web.dev.