  During the last 50 years we have been witness of an extraordinary revolution
in the knowledge and understanding of our star thanks to the development of
Helioseismology, the study of solar oscillations. Similar to what happens on
the Earth during earthquakes, the interior of the Sun is continuously pervaded
by seismic waves which produce small oscillations on the photosphere. These
oscillations bring the signature of several processes which happen in the
interior of the solar structure and the seismic frequencies of the oscillation
modes detected on the solar surface are directly related to physical parameters
of the internal layers crossed by the seismic waves. The study of oscillations
represents, then, the only method to infer directly the internal structure and
dynamics of the Sun. This article will present the general characteristics of
solar oscillations, the main important results and the advances obtained in
stellar physics thanks to the methods of Helioseismology.
