  There has been a surge of interest in effective non-Lorentzian theories of
excitations with restricted mobility, known as fractons. Examples include
defects in elastic materials, vortex lattices or spin liquids. In the effective
theory novel coordinate-dependent symmetries emerge that shape the properties
of fractons. In this review we will discuss these symmetries, cover the
effective description of gapless fractons via elastic duality, and discuss
their hydrodynamics.
