When I save an image from the web to my mac, why does it download a file with lots of random documents?

Hi there, apologies in advance if this isn't the right place for this question. I recently saved two images from Instagram (browser) and IMDB to my mac to use as a reference for a drawing. Both saves created files with lots of documents ending .js and .css. How can I just download an image without this happening? (I'm completely computer illiterate) Thank you.