Not all the energy originates from the sun reaches
to the earths surface what does it mean?

This is due to something known as the Earth's energy budget. This budget accounts for the fact that some of the energy incident on the outer atmosphere of the planet is immediately reflected back into space.

The ozone layer

Explanation:

The ozone layer is a layer in Earth's atmosphere. It protects us from much of the UV rays emitted by the sun. UV rays cause sunburns, eye damage, and even cancer. Without the ozone, Earth would become much warmer and there would be more radiation. Most life on Earth would die without the ozone layer.