  Based on an analytic approach, we present a theoretical review on the
absorption, scattering, and extinction of both dipole scatterers and regular
arrays composed of such scatterers i.e., metasurfaces. Besides offering a
tutorial by outlining the maximum absorption limit for
electrically/magnetically resonant dipole particles/metasurfaces, we give an
educative analytical approach to their analysis. Moreover, we put forward the
analysis of two known alternatives in providing perfect absorbers out of
electrically and or magnetically resonant metasurfaces; one is based on the
simultaneous presence of both electric and magnetic responses in so called
Huygens metasurfaces while the other is established upon the presence of a back
reflector in so called Salisbury absorbers. Our work is supported by several
numerical examples to clarify the discussions in each stage.
