Topological defects are irregularities that occur in ordered systems, such as liquids or crystals, where the arrangement of particles is disrupted. These defects can arise during phase transitions, like when a material changes from a liquid to a solid. Common examples include dislocations in crystals and vortices in superfluids. These defects are significant because they can influence the physical properties of materials. For instance, in liquid crystals, topological defects can affect how light passes through, which is crucial for the functioning of LCD screens. Understanding these defects helps scientists improve material performance in various applications.