Why is other taking up so much space on my iphone?

I recently replaced my old iphone with a new one and I was excited because my old iphone was having a problem where "other" would take up all of my storage. Well, I plugged my new phone into the computer, and now "other" is taking up over 2GB of space on my iphone. I only have 6GB! I really need to fix this problem because it gets to the point where other takes up over half of my space. I already reset and restored it. What is other and how can I delete what is in it? Please help, I can't find anything that says what is stored in other and I'm using less than 2GB of my storage because of this.

May be there some invisible cash or data on your phone, you should clean up occasionally. Hope it helps.