The earth rotates around its axis.  This takes 24 hours.  Half the earth is lit.  This half is having daylight.  The other half of the earth is not lit.  This is called night.

Rotate- to turn around in the same space - as in the Earth spinning around its axis

Axis - an imaginary line running from the North Pole, through the center of the Earth, and out the South Pole.

A year is caused by the revolution of the Earth around the sun.  1 revolution = 1 year.  A year is 365 !/4 days.  The 1/4 days are added together to add one day to February - February 29.  This is known as a Leap Year.

Seasons are caused by 2 factors.

    1.  Orbit of Earth around sun

    2.  Tilt of Earth's Axis - 23 1/2 degrees

When the sun's rays hit directly on a surface, the surface heats up more than when the rays hit indirectly.

Click on the link to see an animated model of Earth's revolution around the sun.