title: What is NSBundle and mainBundle in Objective-C?
body: <p>Regarding Objective-C on iOS application, I read some sample program in the Apple developer website and I found that almost all of the applications contains a word called <a href="https://developer.apple.com/documentation/foundation/nsbundle" rel="nofollow noreferrer">'<strong>NSBundle</strong>'</a> and <a href="https://developer.apple.com/documentation/foundation/nsbundle/1410786-mainbundle" rel="nofollow noreferrer">'<strong>mainBundle</strong>'</a>, and I really don't understand the meaning of this word. What is that?</p>