Complex sentence: In addition to their other properties, all particles possess a quantity called spin (an "intrinsic angular momentum"; despite the name, particles do not literally spin around an axis) which has no correspondence at all in classical physics.
Split into simpler sentences: In addition to their other properties, all particles possess a quantity called spin, an "intrinsic angular momentum". Despite the name, particles do not literally spin around an axis, and quantum mechanical spin has no correspondence in classical physics.