Another name for a B- particle is an electron.
A beta particle is a high energy electron (or positron - an oppositely charged electron) that is released during the radioactive decay of an atomic nucleus. Radioactive decay occurs naturally and some more unstable atomic nuclei, such as those with a surplus of neutrons, are more prone to undergo decay in order to reach a more stable state. In this process a neutron (a non-charged particle in the nucleus) is converted into a proton and electron.
