Complex sentence: The Chandogya Upanishad conceives the whole universal activity of creation as a kind of yajna (sacrifice) where everything is connected; this sacrifice/knowledge is known as the "Panchagni vidya".
Split into simpler sentences: The Chandogya Upanishad conceives the whole universal activity of creation as a kind of yajna (sacrifice), where everything is connected. This sacrifice/knowledge is known as the "Panchagni vidya".