During the daytime, all of it; at night, no part of the Sun. During a short time, during sunrise, only part of the Sun is over the horizon.Note: This is for a specific observer; you can always find a point on the Earth where the Sun is above your head.
If I understand the question as it is written, you are asking what it is called when the moon is between the sun and Earth. That would be called a 'solar eclipse.' If you have the sun blocked by the Earth stopping the moon from getting light it would be a 'lunar eclipse.'
No.
Photosphere
The path of Earth (or other planets) around the Sun is called the planet's orbit.
Because the part of the Earth you are on is not facing the Sun at that time. The earth is continuously rotating, so at any time, part of the Earth is facing the Sun and part is facing away from it. The part facing it is getting lots of light, so it is day time and the part facing away gets less light, so you have darkness and it is night time.
Equator.
Of course not. If it's the center of the Earth, it means that it's part of the Earth, not the sun.
Solar Eclipse
It doesn't. The part of the Earth closest to the sun is the part of the Earth experiencing Winter.
what is the period when a given part of earth is facing the sun
During an equinox, the sun is directly over the equator of the Earth. This causes the length of day and night to be nearly equal all over the world.
No, Earth and the other planets and debris are part of the sun's solar system.
the part of the earth that you are on faces the sun. (the earth rotates on its axis) When it faces the sun, you see it.
you get no sun
The Earth goes around the sun. We are part of the solar system.
The sun does not travel over the earth. The earth turns "under" the sun. As a result, the sun appears to move across the sky a the rate of about 15 degrees per hour
Earth has revolved around the sun.