Sugars are organic compounds that has only carbon, hydrogen, and oxygen. It's the way these atoms are connected that makes each types of carbohydrates different. The 4 basic types of saccharides are monosaccharides, disaccharides, oligosaccharides, and polysaccharides. The simplest of the saccharides are the monosaccharides and disaccharides which are considered as simple sugar. Simple sugar has one or two sugar molecules. A carbohydrate that has one sugar molecule is regarded as a monosaccharide while the one with two sugar molecules that is bonded together is regarded as a disaccharide.
All organisms are made of 4 types of carbon-based molecules which are the carbohydrates, lipids, and nucleic acids. These molecules have various structures and functions, but all are formed around a carbon chains and rings.