Glucose Syrup is made from starch. Depending on where you are in the world, glucose syrup is produced from wheat, barley, tapioca, potato, rice, cassava, arrowroot, sago and maize starches.
In the United States, domestic food manufacturers to call their glucose syrup "Corn syrup" because the source of the starch is almost exclusively from maize.
Although corn syrup is a glucose syrup, glucose syrup is not always corn syrup. They can be interchanged in some recipes BUT they can/do react differently.
The original Rolled Fondant recipe is based on Glucose syrup.
Glucose Syrup is an aqueous solution of several compounds; the proportions of which vary depending upon the source of the starch. Glucose syrup tends to be a thick syrup while Corn syrup [US] is a thinner syrup.
Originally the substitution of one for the other took this into consideration: nowdays, a straight substitution is done ... it depends what you like/choose ...