Magnetotellurics is a geophysical method used to study the Earth's subsurface by measuring natural electromagnetic fields. It involves recording variations in electric and magnetic fields at the Earth's surface, which can reveal information about the geological structures below. This technique is particularly useful for exploring resources like oil, gas, and minerals, as well as for understanding geological processes. The method relies on the principle that different geological materials conduct electricity differently. By analyzing the data collected from various locations, scientists can create models of the Earth's subsurface, helping to identify features such as faults, aquifers, and mineral deposits.