WHERES - WHEREBY

whereas means "while (on the other hand)": "I like cake whereas he hates cake."

whereby means "by which" or "through which": "I devised a method whereby energy is perpetual and lasts forever." The implication is that energy is perpetual through the method, i.e., when you employ the method, you get energy that's perpetual.

Whereas what'she being presented is an operation whereby says (...).