It is unclear what the intent of the author was. If the word is meant to be an acronym then it should be all caps as in 'GEM'. If the word is meant to refer to a brand name or object then 'Gem' is correct but as the word is not used elsewhere in the document, nor is any external reference made, and neither is 'Gem' a common computing term, we have to conclude that the author has mistyped the capital letter and meant to write 'gem'.
A gem is a small precious stone, it appears to be used here to imply that the following information is concise and valuable. A 'gem of wisdom'.