How to extract public info from sites like instagram

When I download a page from instagram the info that is displayed in the web browser like usernames and all that public info are not hardcoded in the html source code.

So how can i get that info? I am a programmer but i dont know web related stuff, i think it should be stored in javascript,php,etc? i dont know but since it is public info anyone can see with the url it must be possible to extract it rigth?

take the following example: https://www.instagram.com/explore/tags/cats/

so there i can see posts about cats, i need to get the info like the usernames of the people who posted those and that kind of stuff.