If I update my iPhone 4 will it erase everything?

It keeps asking me to update it to iOS 6.1.3, but I would download it on my phone. Would it still erase everything? I've never put my iPhone on the computer before. Is that bad? I do the iTunes and everything on my phone.o: if I downloaded that would it erase everything?

If you're not jailbroken, just follow these directions:
Settings > General > Software Update
Then click update, that's the most user friendly way.

It states in the software update what changes will be made (or bug fixes) in the update. For a complete changelog check here http://en.m.wikipedia.org/...#section_4
It's ok even if you update just using your phone.It'll take 10 to 20 minutes tops and no, nothing will be erased

Nope