SITE PERFORMANCE includes several aspects but many components affect how search engines evaluate your website.
Here is another free service from Google that test the speed of your website. Speed is very important for both customer satisfaction. If it takes to long for your website or blog, no one will wait. Search engines use speed as one method for rating your site.
For artists and makers with image heavy sights, speed of downloading the images is a critical factor. Try this "PageSpeed Insights" and see if you can make your web site faster.
This site automatically offers suggestions for improving your site. Some of the suggestions are easy. Others are lessons for the future.
Harriete Estel Berman