It is well known that gapless states have emergent symmetry. If we greatly generalize symmetry to include anomalous non-invertible ones, and beyond, the generalized emergent symmetry may largely characterize gapless states. We may understand a gapless state via its emergent symmetry.  Here, I will use a simple language of conservation law and selection rule to explain the modern understanding of anomalous and non-invertible symmetry, and how generalized symmetry can largely determine low energy properties of gapless liquid states.