Why do we have seasons?

We have seasons because of the Earth's axis -- it is not at the right angles to the Sun's rays, it is tilted. The warmest season, summer, occurs to the hemisphere tilted towards the Sun, receiving more sunlight as the Earth rotates on its axis. The days are longer and the weather is warm because of the extra sunlight. The hemisphere tilted away from the Sun receives lesser sunlight, thus has shorter days and cooler temperature -- it is winter time. The area near the equator is always exposed to the Sun's rays, so it is warm all year round. This means that there is little difference between the seasons.