And what was born from it that was Âditya, the sun. When he was born shouts of hurrah arose, and all beings arose, and all things which they desired. Therefore whenever the sun rises and sets, shouts of hurrah arise, and all beings arise, and all things which they desire.

In plain words: The sun was born from the egg. When it was born, everyone shouted with joy, and all living beings and all the things they wished for came into being. That is why people still cheer and come alive whenever the sun rises and sets.