Short answers, pulled from the story.
Albert Einstein published a paper proposing that light consists of discrete energy quanta in 1905. This idea challenged the dominant wave theory of James Clerk Maxwell from 1865.
Gilbert N. Lewis popularized the term photon for light quanta in a letter published in Nature on the 18th of December 1926. Before this moment scientists used words like quanta or energy elements derived from Latin roots meaning how much.
Photons possess no electric charge and generally have zero rest mass according to current physical theories. Experimental upper limits on photon mass reach values as small as 10^-53 grams.
Sheldon Glashow Abdus Salam and Steven Weinberg unified photons with W plus W minus and Z zero bosons in electroweak interactions. Their work earned them the 1979 Nobel Prize in physics.
Arthur Compton provided experimental proof with scattering experiments in 1922. His work showed photons carried momentum proportional to their wave number.