Dynamic load and unload texture atlas

For targeting multiple display resolution, I focus on using MultiPlatform Toolkit usage.

In which I found following statement in tutorial section for dynamically handling materials.

"Just remember to un-reference your Texture2D from your Material asset in the scene so the scene doesn't try to load the high res texture on a low-end device."

I just can't able to understand what statement trying to say? So please give some guidance on explaining meaning or if you have code then it become beneficial to me.

EDIT:

Also I want to ask about texture loading that author mentioned

 myRenderer.sharedMaterial.mainTexture = Resources.Load("backgrounds/hugeTexture");

Here in the above code what stands for "myRenderer"?