There are two types of shadows of moon:
Umbra: It is represented as the dark grey region of shadow. This is the region where total eclipse is observed on earth as sun is totally blocked by moon.
Penumbra: This region depicted by the light grey shadow of the moon, observes a partial eclipse as only partial rays of sun are barred by moon.
As moon is inclined at a relative 5 degrees and has an elliptical orbit, the apparent size of the moon as observed from the earth varies. The type of eclipse experienced depends upon the distance of the moon from the earth during that period. When the earth comes under the umbra region Total eclipse is experienced. The regions of earth under penumbra rays are partially eclipsed, while when the umbra shadow of moon is not able to reach the surface of earth, Annular eclipse is encountered.
Thus, total eclipse is a rare phenomenon.