“none” often means no background-color, but there is a bg color there, so in this case it refers to no bg image.
“repeat” is for background-repeat
“scroll” is for background-attachment
“0 0” is for background-position, but is kind of irrelevant here, as there is no bg image to be positioned, as are the previous ones.
Of course #E5E5E5 is background-color.
“How does the line background: none repeat scroll 0 0 #E5E5E5; influence design”
It sets the background properties for the element it applies to.
Most of it is useless, though, because there is no background image. It would be better, in this case, just to write:
Most of that line is complete nonsense. The repeat, scroll/fixed and position elements only make sense when there is a background image, but that has been explicitly turned off. You can safely delete “repeat scroll 0 0” from there!