Glycans are carbohydrate components of glycoconjugates, which interact with their receptors; for example, galectins and C-type lectins. The specificity to their receptors makes them the ideal biomarkers that they can be used as a therapeutic target or as a screening tool. We collected and reviewed articles from different databases, which show that glycans play a significant role in several body functions, such as stimulation of the immune system, and can be used in the differentiation among cancer types. They also help in nervous system repair, regeneration, regulation and proliferation. Furthermore, several pathogens like Schistosoma, HIV, Influenza, Candida, and Ebola produce glycoproteins to aid in the invasion via attachment to surface glycoproteins and defend themselves against the host's immune system.