Quasiparticles behave like particles in a few fairly important ways, but aren’t actual particles at all. “Quantized” means, in particular, that each quasi-particle of a particular kind is identical. No particle physicist in their right mind would call a whirlpool a quasiparticle, but the idea is about right. The electrons in atoms are stuck in separate energy levels, and they can only absorb or emit energy corresponding to differences in those levels. This discrete-and-identical set of energy levels is part of why crystals are hard and often transparent (that’s not obvious, it’s just an interesting fact).