Who were Scrooge and Marley and what was their business?

Ebenezer Scrooge is the primary character of Charles Dickens's A Christmas Carol. Jacob Marley was his business partner for many years; Scrooge was the executor of Marley's estate, and Marley appears in the book as the first ghost Scrooge sees. Scrooge is described as Marley's "sole friend," so it can be assumed that Marley was not unlike Scrooge in terms of the relationship he had with the world.
The nature of Scrooge and Marley's business is actually fairly obscure in the context of the text--it isn't described how many employees the business has, nor its particular function. We do see Scrooge busy "in his counting-house." However, the names "Scrooge and Marley" are painted "above the warehouse door." So, the business presumably involves some kind of production floor, with the produce being shipped out of a warehouse, and also an administrative or office element, which is where Scrooge and Bob Cratchit work. However, Dickens isn't any more specific than this.