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

You do know that seasons north of the equator are opposite of the seasons south of the equator, don't you? When it's Summer in North America and Europe, it's Winter in South America and Australia.

Did you know that the Earth is actually closer to the Sun in January and farther away from the Sun in July?

And, ask yourself this question: if the seasons are caused by the distance from the Earth to the Sun, then shouldn't it be Summer everywhere on the Earth at the same time? And, shouldn't it be Winter everywhere on the Earth at the same time?

The tilt of the Earth's axis causes the seasons. And it's not because the tilt causes the northern hemisphere to be closer or farther away from the sun, because that is even less than the change in distance of the entire Earth from the Sun between Winter and Summer. The cause of the seasons is that in January the northern hemisphere is tilted away from the Sun and recieves less direct sunlight and the southern hemisphere is tilted toward the Sun and receives more direct sunlight. In the Summer it's just the opposite.

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The earth tilts on its axis. When the Northern Hemisphere is closer to the sun, it is summer there, and winter in Australia, and vice versa.

the SEASONS in the Southern Hemisphere, south of the Equator ,are reversed from what you are used to. This is due to the TILT of the Earth as it revolves. When we up north of the Equator have winter, we are tilted further away from the sun, and the Southern Hemisphere nations are closer.