ResourcesHelper allows you to get access to your resources by strong typed way.
It automatically generates special static class Resource. Class Resource contains properties to get access to all resources of your project. This class is updated automatically, when you change any resources in any Resources folder.
For example, if you have audio clip CoinsSound.wav in your Resources folder, the class Resource will contain the following property:
public static AudioClip CoinsSound { get; }
In your script you can get access to the audio clip by the following way:
myAudioSource.clip = Resource.CoinsSound;