Complex sentence: Also the term "the" is not a good keyword to distinguish relevant and non-relevant documents and terms like "brown" and "cow" that occur rarely are good keywords to distinguish relevant documents from the non-relevant documents.
Split into simpler sentences: Also the term "the" is not a good keyword to distinguish relevant and non-relevant documents and terms. On the contrary, the words "brown" and "cow" that occur rarely are good keywords to distinguish relevant documents from the non-relevant documents.