Neutrinos are produced by the decay of radioactive elements. After Photons (light carriers) they are the most abundant particles in the cosmos. They propagate over large distances even through solid matter. They have mass, but it is exceedingly small, a tiny fraction of the mass of a proton

There are 3 types of neutrinos, called flavors.One related to the electron, one related to muon and the third type is related to tau.  The main difference between the neutrinos and their “relatives” is that neutrinos are electrically neutral, while the electron, muon, and tau are electrically charged.

Neutrinos are difficult to detect, because they do not
readily interact with other forms of matter. But using
special equipment located in deep underground
laboratories where no other cosmic particles can
penetrate, scientists have detected neutrinos and
discovered some of their properties.

Neutrino oscillation

The earth receives majority of the neutrinos from the
sun itself. For years’ scientists were trying to figure out an anomaly between the observed and the theoretical data of the neutrinos observed.

The studies held by the Super-Kamiokande detector in Japan showed that up to two thirds of number of
neutrinos were missing in measurements performed on Earth.

This was explained by the “metamorphosis” of the 3
neutrinos into one another called neutrino oscillation. This oscillation implies that Neutrinos have mass, however very small.