The Spin-Statistics Theorem is a fundamental principle in quantum mechanics that dictates the relationship between the spin of a particle and the statistical behavior it follows, specifically that particles with half-integer spin are fermions obeying Fermi-Dirac statistics, while particles with integer spin are bosons obeying Bose-Einstein statistics. This theorem is crucial for understanding the structure of matter and the behavior of quantum fields, as it underpins the Pauli exclusion principle and the formation of atomic and molecular structures.