Glycans are complex carbohydrates made up of sugar molecules linked together in various ways. They play essential roles in biological processes, including cell recognition, signaling, and immune responses. Glycans can be found on the surfaces of cells and proteins, influencing how cells interact with each other and their environment. These structures are often attached to proteins and lipids, forming glycoproteins and glycolipids, respectively. The study of glycans is important in fields like biochemistry and medicine, as they are involved in many diseases and can serve as potential biomarkers for diagnosis and treatment.