Explanation:

The earth is tilted at an angle of 23.5 degrees to the normal. This tilt is primarily responsible for the change in seasons on earth. For one half of the year the northern hemisphere is tilted towards the sun and experiences summer season and the southern hemisphere being away from the sun experiences winter.
As the earth revolves around the sun the southern hemisphere gets tilted towards the sun and experiences summer for remaining half of the year.
If the axial tilt is absent there will be no seasonal change. If the Earth was not tilted, the plane of the Earth's poles would always be perpendicular to the sun. The sun would always be just on the horizon 24 hours a day on every day at the poles. But the poles will still remain cold and equator will remain hot.
 Every day would be like what it currently is on the equinox since every location on Earth would have about a 12 hour sunlight days and the noon sun angle would be about the same every day.