Equal Night and Day
Twice a year the axis of the Earth are not pointed away from nor toward the sun. This is known as an equinox. The name comes from the Latin aequus (equal) and nox (night), because around the equinox, night and day are about equal length. Thus, the term equinox can also be used in a broader sense, meaning the date when such a passage happens.
The sun at the North Pole is continuously above the horizon during the summer and continuously below the horizon during the winter. Sunrise is just before the March equinox (around March 19); the sun then takes three months to reach its highest point of near 23½° elevation at the summer solstice (around June 21), after which time it begins to sink, reaching sunset just after the September equinox (around September 24). When the sun is visible in the polar sky, it appears to move in a horizontal circle above the horizon. This circle gradually rises from near the horizon just after the vernal equinox to its maximum elevation (in degrees) above the horizon at summer solstice and then sinks back toward the horizon before sinking below it at the autumnal equinox. The opposite is true at the South Pole.
Without getting into a lot of science, that about sums things up.