If you use a Samsung phone with S Pen and take screenshots, by default the format it saves into is jpg. To change it to png, go to Settings search for "S Pen" > Advanced features > Screenshots and screen recorder > Screen format.
So, why do I want to do that? Because according to this article JPG vs PNG: Which to Choose for Your Website? under JPG vs PNG – the Basic Rule section
Since both JPG and PNG format have their pros and cons, you should get the most out of both of them and play to their strengths.
In practice, that means that you should use .jpeg for photographs, and .png for graphics and screenshots.
I spend a lot of time each day on my phone, in fact I'm writing this entire post on my phone inside Chrome browser. So, having the screenshots in the right format from get-go is awesome.