Difference between Keychain and NSUserDefault?

Question

I am new to objective C, I have created one application in that I have used both NSUserDefault and Keychain to store my user name and

Answer 1

A keychain is an encrypted container that holds passwords for multiple applications and secure services. Apple Inc. uses keychains as password management system in Mac OS and iOS.

NSUserDefaults Provides a way for application behavior customization based on user preferences. Belongs to the Foundation framework for Cocoa and Cocoa Touch.

I got this from Tag Information of NSUserdefaults and keychain