Just like electrons and their heavier counterparts, muons and tau particles, neutrinos belong to the leptons. Neutrinos on the other hand are not charged, and only experience the weak nuclear force.
Neutrinos originate in nuclear reactions and in the core of stars such as our sun.
Since they hardly leave any tracks, it is not simple to do measurements on neutrinos. To detect them we need huge and heavy detectors. Here they first pass through a so called veto counter, which only reacts to charged particles and does not signal a passing neutrino. When this counter reacts, we ignore the interactions in the detector. Sporadically, a neutrino interacts with an atomic nucleus in this emulsion and produces a muon.