what is 'OTHER' on iPhone

Hello,

I have an iPhone 4 that runs great and has no problems. It syncs up with iTunes just fine but the category 'OTHER' is taking up 3GB of space. What is considered 'OTHER' and how do I reduce how much space it takes up?! I attached an image to show you how much space its taking up. Please help!!

Thank you.

"Other" is all of the data on your phone that is not music, videos, photos, apps, or books. So it includes iOS metadata, email messages, text messages, notes,voice mails, calendars, Safari cache, Siri cache, iPod database index, plus all of the data from all of your apps. And probably a few things I missed.