Trapping sets are a key concept in the field of error-correction coding theory. In coding theory, trapping sets are sets of variable nodes in a Tanner graph that cause errors to propagate and become trapped, making it difficult for the code to correct those errors. Trapping sets play a crucial role in understanding the performance of iterative decoding algorithms in low-density parity-check (LDPC) codes and other types of error-correction codes. Researchers study trapping sets to analyze and improve the error-correction capability of coding schemes.