Spin-orbit coupling is a phenomenon in quantum mechanics where the spin of a particle interacts with its orbital angular momentum. This coupling arises from the interaction between the particle's magnetic moment (spin) and its motion around a central potential. Spin-orbit coupling has significant effects on the behavior of electrons in atoms, leading to fine structure splitting in atomic spectra and affecting the properties of materials. Understanding and controlling spin-orbit coupling is crucial for various applications in areas such as quantum information processing, spintronics, and topological materials.