What is the difference in what they are made of?
Please cite sources. Web sources would be great.
Both are dissacharides, but table sugar is sucrose and that's made up of glucose and fructose. Lactose, or milk sugar, is made up of galactose and glucose.
Well, both are essentially made from 2 units of glucose joined together to make a 'disaccharide' although in the case of table sugar it is one unit of glucose and one unit of fructose.
The real difference is in the chemical structure of the two is this single fructose. I recommend wikipedia as it shows chemical structures.