The Earth orbits the sun once every 365 days and rotates about its axis once every 24 hours. Day and night are due to the Earth rotating on its axis, not its orbiting around the sun. The term 'one day' is determined by the time the Earth takes to rotate once on its axis and includes both day time and night time.
Why Earth has sequences of seasons.
Earth has seasons because its axis is tilted. Earth's axis is always pointed in the same direction, so different parts of Earth get the Sun's direct rays throughout the year. For example, in summer, the Sun's rays hit that region more directly than at any other time of the year
