As illustrated in image above, Assume that you have to access & display the Application version name.
Or While making a web-service call, you have to pass the version of the application, so that server can know, which version of app is sending the request.
To Access Application Version, Use following line of code.
NSString *strAppVersion = [[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleVersion"];
NSLog(@"Applicatin version is %@",strAppVersion);
Hope that helps.