Why do we have different seasons?

The Planet Earth during winter is about 5.000.000  km (3.106.855 miles) closer to the Sun than in summer, and yet the Earth is warmer in summer than in winter.
How is this possible?
The distance between the Earth and Sun does not make any difference, but the main factor is the Earth's axis tilt, as the Earth revolves around the sun. 
Scientists have determined that the Equator is tilted for 23 degrees from the Earth's orbit around the Sun.
While the earth revolves around the sun, its axis always remains in the same position toward the North Star. Therefore, one part of the year the North Pole is tilted toward the sun, and in the other part of the year it is in dark.
When the North Pole faces the sun, there is summer in the northern hemisphere, and when it is in the darkness, in the northern hemisphere occurs winter.
In the southern hemisphere that is reverse.
The differences in the seasons result from the fact that during the winter sun's rays fall on the Earth under the lower angle, and in the summer the angle is bigger.
Rays that have lower angle, provide less heat for two reasons. 
The first is that their heat is distributes to much of the Earth's surface, and the second is that they lose more heat on their way through the atmosphere.

Other factors that affect climate

Other factors that affect climate are: distribution of land and sea and elevation, water stabilizes and prevents large changes in temperature.
The land does not collect heat as the ocean does and therefore significant temperature changes can occur over large expanses of land.
With the increase of altitude, the air becomes thinner and can’t absorb as much heat it does at sea level. Therefore in increased altitude the temperature drops.