I thought seasons changed with revolution of earth around Sun on its orbit and day/night by rotation?

When I was in 5th grade , Noah and I went to the same school, we were shown a film about this. The sad thing is 47% of Harvard Grads think as you do. Ranokin is correct.

The reason for the seasons is actually quite simple.

The earth rotates on a slightly tilted axis, due to this, the sun shines on different parts of the planet in different intensities. for example, during summer in the USA, we are directly pointed towards the sun during the day. Imagine a flashlight pointed directly towards a flat surface, the light covers a small area, and is very concentrated. Now, at the same time the USA is having summer, Australia is having winter, because the suns light only hits it during the day at an angle. imagine the same flashlight pointed at a flat surface, only now the flashlight is shining at an angle. Notice how the light is now cast over a much larger area, but it is less concentrated, resulting is much colder temperatures.

The axis of the earth doesn't point straight up, it is tilted. This means that in July (for example) the northern hemisphere is pointing towards the sun, and in January it is pointing away from the sun. The southern hemisphere obviously points in the opoosite direction, so that is why Australia has summer in December. It is the same for any temperate country south of the equator. This also explains why the Artic circle has permanent night for months during winter and permanent day in the summer.