An eclipse is an astronomical event that occurs when an astronomical object or spacecraft is temporarily obscured, by passing into the shadow of another body or by having another body pass between it and the viewer.
You can learn how solar and lunar eclipses occur by observing this model – moving the moon and earth in their respective orbits.
Please note that moon’s orbit around the earth and earth’s orbit around the sun are not in the same plane.
Think what will happen if they are co-planar.
On a New Moon Day (Amavasya or Amavasai), the moon comes in between the sun and the earth.
For a viewer from a point on earth, if a part of the sun is concealed by the moon orbiting around the earth, then it is solar eclipse.
Eclipse is Total, if the whole of apparent image of the sun is temporarily covered by the orbiting moon.
Eclipse is Annular, if the moon is able to cover a smaller circle inside the sun.
Eclipse is partial, if only a portion of the sun is covered.
Total solar eclipse is a very rare occurrence.
On a Full Moon day (Poornima or Pournami), the earth comes in between the sun and the moon.
Viewed from a point on the earth, if the earth’s shadow falls on the orbiting moon, then it is lunar eclipse.
Eclipse is Total, if the moon is covered fully by earth’s shadow at any point of time during the eclipse.
Eclipse is Partial, if the moon is covered partially.