We'll begin by making some structural sense of those terms.
Sugars are small molecules which belong to the class of carbohydrates.
As the name implies, a carbohydrate is a molecule whose molecular formula can be expressed in terms of just carbon and water. More complex carbohydrates such as starch and cellulose are polymers of glucose. We'll look at them in more detail next time. Beyond that, though, there's another important structural feature. Look at the disaccharide and focus on the oxygen which links the two rings together.