Short answers, pulled from the story.
The weak interaction, also called the weak force or weak nuclear force, is one of the four known fundamental interactions, alongside electromagnetism, the strong interaction, and gravitation. It is the mechanism responsible for the radioactive decay of atoms and takes part in nuclear fission and nuclear fusion.
The weak interaction is called weak because its field strength over any set distance is typically several orders of magnitude less than that of the electromagnetic force, which is itself orders of magnitude weaker than the strong nuclear force. Its coupling constant is tiny compared with the strong interaction's value of about 1.
The weak interaction is the only interaction that lets quarks swap their flavour, mediated by force-carrier bosons. In beta-minus decay, a down quark in a neutron changes into an up quark, converting the neutron into a proton and emitting an electron and an electron antineutrino.
Sheldon Glashow, Abdus Salam, and Steven Weinberg developed the electroweak theory around 1968, showing electromagnetism and the weak interaction to be two aspects of a single force. They were awarded the 1979 Nobel Prize in Physics for the work.
The weak interaction violates parity because it acts only on left-handed particles and right-handed antiparticles, as described by the V minus A theory. Chien Shiung Wu and collaborators discovered this parity violation in 1957, and Chen-Ning Yang and Tsung-Dao Lee received the 1957 Nobel Prize in Physics for proposing it.
The existence of the W and Z bosons was directly confirmed in 1983, matching the masses the electroweak theory had predicted beforehand. These carrier particles have masses of approximately 90 GeV/c squared and are short-lived.
The weak interaction makes radiocarbon dating possible because carbon-14 decays through the weak interaction into nitrogen-14. Most fermions decay by a weak interaction over time, and the same process underlies tritium luminescence and betavoltaics.