The reason you never see the far side of the Moon is that the Moon is tidally locked to Earth. This means its rotation period is the same as its orbital period around Earth, so the same hemisphere always faces us while the opposite hemisphere (the far side) remains out of view from Earth. In more detail:

• Synchronous rotation: The Moon rotates once on its axis in about the same time it takes to orbit Earth (roughly 27.3 days sidereal, or about 29.5 days proportionally to the phases). Because these timescales match, the near side is continually oriented toward Earth.
• Far side timing: The far side does receive sunlight and has days and nights, just like the near side; it’s not perpetually dark. The term “dark side” is misleading; a more accurate name is the “far side,” since it’s simply the side we don’t see from Earth.
• Earth’s perspective: From our vantage point, we see the Moon’s longitude-fixed face; as the Moon orbits Earth, the Earth–Moon system keeps the same hemispheres oriented similarly due to tidal interactions.

Additional nuances:

• Earthshine can illuminate the far side slightly during certain conditions, but that doesn’t change the fundamental geometry of visibility from Earth.
• The far side has distinct geography (craters, basins, and maria) that we’ve studied via spacecraft flybys and orbiters, such as the Soviet Luna missions and NASA’s Lunar Reconnaissance Orbiter.

If you’d like, I can tailor this explanation to a specific audience (high school, curious layperson, or science class) or add a simple analogy or a diagram description to visualize tidal locking.