The Moon revolves around the Earth in a period of about 27 days; it also rotates once on its axis in the same time and so it always keeps the same face towards the Earth. This phenomenon is known as captured rotation.
Inspite of the fact that the Moon’s axial rotation is equal to its period of revolution round the Earth, we can actually examine more than the half of the total surface. The reason is that Moon travels round the Earth in an ellipse, not in a circle since it takes elliptical path, the rate of axial spin remains constant, whereas orbital velocity changes and moves fastest when closest to us.
We can thus see a little round alternate edges of the Moon. Also, the lunar orbit is tilted with reference to ours, so that the Moon is sometimes north and sometimes south of the mean plane, enabling us see some way beyond alternate poles. These minor shifts, known as Librations, allow us to examine four-sevenths of the total surface. The remaining three-sevenths of the Moon is permanently hidden from our inquiring eyes.
The time taken for the moon to turn on its axis once and the time taken for it to revolve once around the earth are the same. Hence the moon shows us the same face every night. This is called synchronisis rotation or captured rotation.