Revolution:The earth revolves on its own axis and rotates around the sun at the mean time. When the moon runs into the shade part of the earth. The area inside the moon and the earth is shadowed by the earth. The moon seems missing a part seeing from that area. Now the sun, earth and moon are almost in the same line.
Solar Eclipse: When the moon runs into the middle of the sun and earth, if the three are in the same straight line, the moon will block the lights emitting from sun to earth. The black shadow covers the earth. Then solar Eclipse happens.
With the assembly of this mode, the above complicated phenomenon will become very easy to learn.