Purpose of plane/grid in scene?

I'm not sure what you actually call it, but what are some common scenarios where I'd need to think about the "gray grid" that seems to live in the middle of my scene? It looks like a floor and stretches out forever and is default in a new scene.. Is it there just for visual reference purposes?

 

Yes, it's just there for visual reference purposes.

 

Ok, cheers! Do you usually place everything on the plane or do you sometimes prefer to forget it entirely (and if so, could we hide it?)

 

I don't know. The plane represents Y=0 and I find that very useful. But in cases where I don't care, I just ignore it.

 

The grid is so faint, I barely notice it. Each cell is one unit (1 meter) square and is supposed to be used for layout.

If you require a more robust x,y,z grid system try ProGrids. It's free and now part of Unity.