A pile cap is a thick concrete mat that sits on top of a group of piles, which are long, slender columns driven deep into the ground to support a structure. The primary purpose of a pile cap is to distribute the load from the building evenly across the piles, ensuring stability and reducing the risk of settlement. Typically used in foundations for large buildings or bridges, pile caps help transfer the weight of the structure to the piles below. They are designed to withstand various forces, including vertical loads and lateral forces from wind or earthquakes, making them essential for safe construction in challenging soil conditions.