nk as I understand it, Instagram is kind of Twitter or Facebook but for images only, in other words a way of recording pictorial bites of your life with very brief comments. You have followers as in Twitter. I signed up for Instagram because I wanted to see my daughter's pictures, and now I like it and use it to record images. It is instant, that's the fun of it. See it, like it, photograph it, post it.
I follow about 6 people - my favourite is a photographer guy who works for National Geographic. It's a wonderful way of seeing the world (depending on who you follow).