Just as there are various kinds of sugar in the market, white and caster sugar are two common examples. One of the major differences between white and caster sugar is how they feel when you touch them. Caster sugar is not as thick as white sugar; when you touch caster sugar, it is finer than white sugar.
Caster sugar is just like having a sugar in the form of powder. As a result of its fine nature, caster sugar dissolves more readily than white sugar. The granules in white sugar can be easily separated because they are not as thin as caster sugar.
On the other hand, the granules in caster sugar cannot be easily separated. Caster sugar is mostly used in beverages since it can dissolve more quickly than white sugar. White sugar is mostly used for baking, and also as drinks sweetener simply because of the flavor it adds when mixed with drinks.