Can iphone 5 take photo in .png format

So my friend sent me 3 images they had taken on their phone, 2 came as jpgs but one came as a .png image.  I was skeptical as they were different formats.

Is this even possible and if not how could an image be a .png ? 

read somewhere this could be a screenshot/grab but when i tried that myself to emailed to self through gmail app it still appreared as a jpg

the email also came from someone using gmail

Thanks in advance