Idiot's guide to PageSpeed Insights - what's your favorite article for dummies?

I need the best breakdown of PSI and core web vitals there is. Google's own 'About' page that is linked from the reports still reads like an academic book. It's not written in simple enough language enough for me, explaining everything. I'm just a web designer / SEO specialist as one of my MANY marketing tasks - I need to learn on the job!

What's your favorite?