Magnetoresistance is a property of certain materials that causes their electrical resistance to change when exposed to a magnetic field. This effect occurs because the magnetic field influences the movement of charge carriers, such as electrons, within the material. As a result, the resistance can either increase or decrease depending on the material and the strength of the magnetic field. This phenomenon is utilized in various applications, including hard disk drives and magnetic sensors. In these devices, magnetoresistance helps improve data storage and retrieval by allowing for more precise detection of magnetic fields, enhancing overall performance and efficiency.