Cyanocobalamin is the most common and widely produced form of the chemical compounds that have vitamin B12 activity.
For example, the hadron constituents of atomic nuclei, neutrons and protons, have charges of 0 e and +1 e respectively; the neutron is composed of two down quarks and one up quark, and the proton of two up quarks and one down quark.
Sometimes, when an atom doesn't have the 'right' number of neutrons, it becomes unstable and shoots out sub-atomic particles, a common one being the electron. What is happening is that one of the neutrons in this neutron-enhanced version of the atom, is changing into a proton plus an electron (plus a zero mass particle called the anti-neutrino, but we can chat about that some other time).