  The pion-nucleon sigma term is a quantity involved in many important aspects
of particle and nuclear physics. In this review I show its origin and how it is
connected to important questions as the origin of mass of the ordinary matter,
studies of dark matter detection and nucleosynthesis. I mention the most common
methods used to obtain the sigma term, and comment on the extracted values. As
it is shown, the accepted value of the sigma term has been moving from
relatively low ($\sim 40$ MeV) to larger ones ($\sim 60$ MeV) until today,
where this controversy still persist.
