Every time I've interacted with it I've found it extremely obnoxious, it is very strongly oriented to capture users within it's network and actively tries to avoid letting users do anything while logged out or to get a raw image.

My most frequent interaction with Pinterest is excluding it from Google Image Search results.

Pinterest is really big in the DIY space. It's success is more easily explained hand in hand with Etsy rather than any social media.

Different-ish.

There's a recommendation system that I think is pretty good and people can collect other people pictures/pins in their own collections.

I don't think there is any emphasis on influencers or at least from my casual usage I don't see any. I think this is in part because people can collect other people's pins/pictures into their own collection.

It is generally good for 'mood boards' and other designer type stuff where you want to collect a bunch of images to fit a theme or inspire an idea. In my experience it's been more popular with women and crafty/DIY types.

Pinterest is huge in the Architecture and Design community as a place to organize project inspiration and ideas.