An NSBundle object locates your app in the local file system so you can access resources and use them in your programs.
[NSBundle mainBundle] returns the object for your app. When you use the pathForResource: ofType: inDirectory: method, you can easily find the path to those resources. For example, to find the Default.png file in the top level of an iPhone or iPod touch application, use:
[[NSBundle mainBundle] pathForResource:@"Default" ofType:@"png" inDirectory:@""]]. Couldn't be simpler.
Skip the type argument (use @"") for resources without extensions.