The B-H curve, also known as the magnetization curve, illustrates the relationship between magnetic field strength (H) and magnetic flux density (B) in a material. It shows how a material responds to an external magnetic field, indicating how much magnetization occurs as the field strength increases. This curve is essential in understanding the properties of magnetic materials, such as ferromagnets and paramagnets. The shape of the B-H curve can reveal important characteristics, including hysteresis, which describes the lag between the applied magnetic field and the material's magnetization response.