Type-II superconductors are materials that can conduct electricity without resistance below a certain temperature, known as the critical temperature. Unlike type-I superconductors, which completely expel magnetic fields, type-II superconductors allow magnetic fields to partially penetrate them in specific regions called vortices. This unique behavior enables them to maintain superconductivity in stronger magnetic fields. These superconductors are often made from complex compounds, such as niobium-titanium or high-temperature superconductors like YBCO (yttrium barium copper oxide). They are widely used in applications like MRI machines and particle accelerators due to their ability to carry large currents and operate in high magnetic fields.