In this thesis, we study a combinatorial parameter of code called stopping set that has an important role in iterative decoding of LDPC codes on the binary erasure channel. In study of stopping sets, the concepts like stopping distance and stopping redundancy are presented and we study these parameters for linear codes in particular for Simplex codes, Reed-Muller codes and the binary Golay code. Also, a formula for enumeration of stopping sets of arbitrary size in parity-check matrices of linear codes especially in parity-check matrix of Hamming code is given. Finally, the new results about stopping sets and enumeration of these sets in parity-check matrices with constant weight columns are presented.