How is solar eclipse caused?

A solar eclipse occurs when the earth is covered by the shadow of the moon. If we see the sun from that shadow, which was cast by the moon, the sun would visible partially or it may not be visible.  This occurs when the moon comes in between the sun and the earth. 
 

When the sun, moon, and earth aligned in a straight line, the moon blocks the sun rays entering into the earth, forming a shadow on the earth. When we try to see the sun at that time the sun might be visible partially or it may not be visible completely. This is called a solar eclipse.