The abbreviation e.g., standing for the Latin exempli gratia, or “for the sake of example," means exactly that -- a series of examples: "large dogs, e.g., Saint Bernards and Great Danes." The abbreviation i.e., standing for id est, or "that is," explains the subject you have mentioned: "large dogs, i.e., those over 3 feet tall and weighing over 50 pounds." (The Book of Answers, by Barbara Berliner)