Final answer:
A neutrino is a virtually massless and chargeless particle produced in the Sun's fusion reactions. Moving at speeds near the speed of light, neutrinos rarely interact with matter and are part of the proton-proton chain reactions that power the Sun.
Step-by-step explanation:
The nearly massless and chargeless particle that is one of the byproducts of fusion reactions in the Sun is known as a neutrino. Neutrinos are fundamental particles associated with the weak nuclear force, and they have such a tiny mass compared to an electron that they're often considered to be virtually massless. These particles move at speeds close to the speed of light and interact with matter on a very rare occasion. Due to this weak interaction, neutrinos can travel through substantial amounts of matter, such as light-years of rock, without being likely to collide with anything. In fact, a stream of neutrinos from the Sun constantly passes through our Earth, and hence our bodies, completely unnoticed.
The proton-proton chain, a series of thermonuclear reactions, is the main source of the Sun's energy. During these reactions, two hydrogen atoms fuse to form deuterium, emitting a positron along with a neutrino. After generation near the Sun's core, neutrinos make their way to the Sun's surface and escape into space within about two seconds, due to their weak interaction with other matter.