  We present a unified description of spherical discontinuity surfaces in
General Relativity based on two parameters: mass function and surface
permeability. The surfaces considered are: \textit{Impulsive fronts}, massive
permeable layer; \textit{Surface layers}, massive impermeable layer;
\textit{Shock fronts}, massless permeable surface; and \textit{Boundary
surfaces}, massless impermeable surface. We derive the exact jump conditions
for the physical variables across all these surfaces. Finally, we discuss the
quasi-static approximation from studying slow hydrodynamic processes involving
discontinuity surfaces.
