a marble run is a course made for a small ball (or marble) and its aim is to travel from the start to finish with no flaws
to make a marble run you need a small ball and that is it after you make a course using anything you can find (see:rube Goldberg)
a marble is a small glass ball and is more commonly used for the game 'marbles'
A German glassblower invented marble scissors, a device for making marbles, in 1846. The first mass-produced toy marbles (clay) made in the US were made in Akron, Ohio, by S. C. Dyke, in the early 1890s. Some of the first US-produced glass marbles were also made in Akron, by James Harvey Leighton