A coal seam is a layer of coal that is found within the Earth's crust. It forms from the accumulation of plant material that has been buried and subjected to heat and pressure over millions of years. Coal seams can vary in thickness and can be found at different depths, making them important for mining operations. Coal seams are typically located in sedimentary rock formations and can be extracted through various mining methods, such as surface mining or underground mining. The coal obtained from these seams is used primarily as a fuel source for electricity generation and in various industrial processes.