A t-design is a specific type of combinatorial design used in statistics and experimental design. It consists of a set of points and blocks, where each block contains a fixed number of points, and every subset of points of size t appears in exactly one block. This structure helps in organizing experiments efficiently, ensuring that all combinations of factors are tested. These designs are particularly useful in block designs and Latin squares, where researchers want to control for variability among experimental units. By using t-designs, statisticians can improve the accuracy of their results while minimizing the number of experimental runs needed.