If I update, restore Iphone, IOS will change, get newer?

Like if I have IOS 5 it will be IOS 6?

Yes, you are updating, so you will get the new version of the iOS. You don't need to restore to do that.

If you restore your mobile, it will erase everything and update to the latest supported iOS for your iPhone.

Restore means you get fresh version of previous OS but if you update the device, you will get the currently available version of the OS. But in both conditions, you will have a fresh OS in your iPhone.

Well yea. That's what an update does.