I'll admit to also not knowing.

My understanding, and perhaps I'm wrong, is that:

1) It's like Flickr, except it's an app on a phone rather than a web page

2) It uploads directly from the phone rather than you having to upload

3) I believe there's some type of photo effects studio

And that's the sum of my understanding, but it still doesn't add up to much... what else is there that I'm missing?

PS: I feel I've just done the tech equivalent of one-line movie synopses: http://johnvey.com/features/movies Totally failing to express what you might feel when you use the app, my knowledge of Instagram is really just what I've heard... if there's a big warm fuzzy thing I'm missing please share.