Any atom that has 2 protons and 2 neutrons in its atomic center.That atom is called an alpha particle.The nucleus of an alpha particle is similar to the nucleus of helium.
High energy and high speed electrons and positrons are called beta particles.
Positron can also be called antielectron.Positron is a kind of antiparticle of electron.
The positron has the same mass as the electron.But the positron has an opposite charge against the electron.
Beta particles are released by radionuclides from their nuclei.
Beta decay is observed in nuclei that contain too many neutrons to achieve stability.
3) gamma particle
A photon is produced after the decay of radionuclides.That photo is called a gamma particle.
Gamma particles are the most powerful particles in the electromagnetic spectrum.