  The evolution of low- and intermediate mass stars at the onset and during
core helium burning is reviewed. Particular emphasis is laid on structural
differences, which may allow to identify a star's nature and evolutionary phase
in spite of the fact that it is found in a region of the
Hertzsprung-Russell-Diagram objects from both mass ranges may populate. Seismic
diagnostics which are sensitive to the temperature and density profile at the
border of the helium core and outside of it may be the most promising tool.
