Dextrose or corn sugar is readily fermentable and settles out into a firm layer which makes racking easier. It is still called for when making most beer kits. It will impart less of a "cidery" taste to beer than refined table sugar will. Glucose is the sugar present, and glucose or brewer's adjunct is just a high-grade form of corn sugar. It is easy for yeast to metabolize and adds nothing but alcohol (no cidery or off flavours) to your brew when used in moderation (less than half the fermentable sugars).
For a good rule of thumb, never add more sugar than the weight of the can of malt being used. Sucrose (white table sugar) is formed of one glucose and one fructose molecule. It is easily fermentable, but is much more likely to contribute to that dry, cidery flavour of not-so-good homebrew. If you must use sugar, use dextrose corn sugar instead.
Ingredient for Recipes:
Dextrose Corn Sugar can be used in almost all Beer Recipes.