The axis of the earth is the imaginary line that runs from the North Pole to the South Pole. During different times of the year, the axis tilts in different directions. In the winter, the North Pole tilts farther away from the sun than it does in winter, so the northern hemisphere (aka: Half) of the earth spends more time in the shadow of the earth (night time) than it does in sunlight (daytime).
The seasons ,spring, summer, autumn and winter are caused by the tilt of the earths axis and as the earth makes its yearly journey around the sun different parts of our world are either tilted towards the sun or tilted away from the sun. This causes the differences in the lengths of sunlight/daylight hours with very predictable results.