A beta particle is made up of a positron or an electron that has been emitted when an atom undergoes beta decay. Beta particle emission is different from alpha and gamma radiation, which consist of helium nuclei and high-powered photons respectively.
The two types of beta particle decay are positive or negative depending on if it is a positron or electron that is emitted. During the process of positron decay, one of the protons in the atom's nucleus is converted into a neutron and gives off both a positron and an electron neutrino. When negative beta decay occurs, one of the neutrons in the atom's nucleus is converted into a proton and gives off both an electron and a positron neutrino. In both cases, the atom changes elements depending on if it has lost or gained a proton.
Although the beta particle itself is only an electron or positron, they are referred to as beta particles to differentiate between the particles that are emitted during radiation and the electrons that are part of the atom.
Beta particles are able to penetrate deeper into organic material than alpha particles (although less so than gamma rays). As a result, these particles are more likely than alpha particles to cause radiation damage in living things. Radiation treatment for certain types of cancer uses the emission of beta particles.