Parity refers to the symmetry of physical systems under spatial inversion, where coordinates are transformed to their negatives. In weak interactions, parity is violated because these interactions involve a combination of vector and axial vector components, leading to an asymmetry not present in electromagnetic interactions, which conserve parity. The term "maximal violation of parity" indicates that the effective interaction is a complete combination of vector and axial vector effects, resulting in equal contributions from both. This contrasts with other interactions where parity is conserved. Understanding these concepts is crucial for grasping the fundamental differences in particle interactions.