A horsham stone is a type of building material that is made from a special type of sandstone found in the town of Horsham, England. It was often used in the past for building houses, walls, and other structures. Picture a bunch of rocks that look kind of like sandy bread. These rocks are mined from the ground and then cut into rectangular blocks that can be used in construction. Horsham stone is popular because it looks pretty and can last a long time without breaking down. Think of it like playing with really strong sand blocks!