These antiparticles tend to be rare in nature. When a particle and its antiparticle come in contact, under the right conditions, they annihilate each other, typically in a release of photons appropriate to preserve energy and momentum.
Typically, an antiparticle is named the same as the regular particle, but with an "anti" preface. The antiparticle of the proton is the antiproton, while the antiparticle of the electron neutrino is the electron antineutrino. The exception to this is the electron itself, which has the positron for an antiparticle. (The reason why the antiparticle of the electron neutrino is not called the positron neutrino is anyone's guess.)
Discovery of antimatterAntimatter was originally discovered by the physicist Paul Dirac, when he was developing the quantum theory of the electron. In constructing the equation that represented electrons in quantum physics, he realized that the equation allowed for another type of particle which had exactly the same properties, but opposite charge.
A few years later, this particle was discovered and later named the positron.