Sugars are a type of carbohydrates. They provide the body with the energy that our organs and muscles need to function. 1g of carbohydrates (and therefore 1g of any sugar) contains 4 calories, as does 1g of protein. 1g of fat contains 9 calories.
Although by saying “sugar” people often refer to sucrose, i.e. table sugar, made from sugar cane or beet, there are other types of sugars, such as fructose (sugar found in fruit juices and honey), glucose (sugar found in vegetables and fresh fruit), lactose and galactose (sugars naturally present in dairy), and maltose (sugar that the human body generates when digesting starchy food).
Sugar is also made from starch. This sugar (called “glucose-fructose syrup” or “fructose-glucose syrup”) comes in a liquid form. It has a similar composition to sucrose and is often used as an alternative to table sugar in some food products.