How to get a good picture off my ipod/iphone?

So i'm going on instagram and i see these people who have great pics with like a drink or something and its like the main object and the rest is sorta blurred… My questiong is how do they do that i know they use the camera too but how do you do iton your iphone please help me i love photos!

If you have an iphone then when you're taking the picture, tap on the object you want to be clear to focus it, but there's also an effect on instagram to blur the background so maybe they used that