Nutritional breakdown per 100g
  of which sugars99g

Demerara sugar is a pale and mildy flavoured sugar named for the region of Guyana from which it originates

Demara sugar is characterised by large crystals and a crunchy texture. As such it is often used in recipes for it's physical properties as much as for its sweetness and it can often not be easily substitued with other sugars because of that. A typical use would be to make crumble toppings where in addition to sweetness it provides texture. In that instance a suitable substitute might be brown sugar but chages would need to be made to the recipe to compensate for the texture, for example a typical subsistition might be to replace demarara in a crumble topping with a mixture of brown sugar and oats, the oats provide the texture which would normally have been provided by the demarara sugar. This problem with that subsititation is that brown sugar is hygroscopic containing a large amount of water making for a soft sugar hence the need to compensate for the texture.