The moon revolves around the earth in a fixed orbit.

The moon does not have its own light.

Sun gives light to the moon.

When the moon is between the earth and the sun, we cannot see the moon at all.

This is because the side of the moon facing the earth does not get sunlight.

This is called the new moon.

After 2 to 3 days, we can see some part of the moon.

This phase is called the waxing crescent.

As the moon is gaining light, that is, expanding in illumination, we use the term waxing.

About a week after the new moon, we can see half of the moon.

This phase is called first quarter.

Two or three days after the first quarter, more than half of the moon is visible.

This phase is called the waxing gibbous.

About two weeks after the new moon, we can see the full moon.

This is because the full side of the moon facing the earth gets sunlight.

Now, the moon begins its return journey from the full moon to the new moon.

The next phase is called the waning gibbous.

As the moon is now losing light, that is, decreasing in illumination, we use the term waning.

The next phase is the last quarter followed by the waning crescent.

When the moon comes back between the earth and the sun, it enters the New moon phase again.

Number of days between 2 new moons is 29 as the moon takes approximately 29 days to revolve once around the earth.

These changing shapes of the moon are called phases of the moon.