A hysteresis loop is a graphical representation of the relationship between an external force and the resulting response of a material, often seen in magnetic or elastic systems. It illustrates how the material's state depends not only on the current conditions but also on its past history. This loop typically shows two curves: one for increasing force and another for decreasing force, indicating energy loss during the process. In magnetic materials, the hysteresis loop demonstrates how the material retains magnetization even after the external magnetic field is removed. This phenomenon is crucial in applications like transformers and magnetic storage devices, where energy efficiency and material behavior are essential for performance.