Beta Particle is an electron (negative charge) or positron (positive charge) naturally released by certain unstable atomic nuclei during the beta decay process of nuclear disintegration.
Beta particles have a mass that is half a thousandth of a proton’s mass and bear either a single electron or a positron. They can achieve relativistic speeds (close to the speed of light) because they have a limited mass that can be emitted with high energy.
Their light density ensures that, by contact with matter, they lose energy easily and have a haphazard direction as they pass by air or other material.
Beta particles are often less ionizing than alpha particles and, for a given amount of energy deposition, usually do less harm. Usually they have ranges of tens of centimeters in the air (dependent on energy) and a few millimeters in materials.