Instagram’s explore tab is the one where you can see photos and videos which are popular, trending, or featured sorted by Instagram algorithm. Now Instagram is working on making the experience simple, elegant and seamless.
Previously explore tab had randomly placed popular photos and videos but in new design its all sorted into categories like sports, photography, people, etc. Seems like the sorting is done by hashtags, but images with hashtags also get sorted perfectly, probably because Instagram is using some kind of image recognizing AI. Below that is popular hashtags segment followed by randomly sorted images and videos.
Instagram is always trying to make experience better for its users. For me Instagram has the best ui and UX design compared to other social medias.