(*note that the term "holographic projection" is taken from the program; the way the effect is depicted in the show is not remotely consistent with real holography, which is a specific process for creating three dimensional images. The "hologram" depicted in the series is more like a three dimensional projection, though in this case the science is never made entirely clear, and it may be they intended the term "hologram" to be a form of slang.)
The series very rarely addressed real historical events, though it often used its "ordinary people" plots to address particular social, political, and spiritual issues. Only once in the 97 episode run did Sam "leap" into a known historical figure (Lee Harvey Oswald). Other episodes depicted Sam dealing with social issues during particular periods, such as civil rights, racism, the Vietnam War, and the American/Russian Cold War. The series strongly favored messages of tolerance and understanding others, aided in large part by the story format, which forced the protagonist to literally "walk in another man's (or woman's) shoes."
The series (created by Don Bellisario) was somewhat unnusual in that it had a science fiction concept, but little science or fantasy oriented storytelling, instead focusing on the personal journeys of Sam Beckett and those he encounters. Even in its final episode, the show refused to resolve many of its own technical and holistic questions, choosing instead to leave things open-ended and focus tightly on the series' overarching message: that a single person can change the world one life at a time.
The final episode was in fact intended to be an end-of season cliffhanger, but after the series was not renewed by the network, the show was reedited to create the final episode. This accounts for some of the ambigious nature.
Other uses of this term include: quantum leap, phenomenon