Eagle, birdie and bogey are all golf terms for the number of strokes required to complete a hole. They are relative to par, which is the number of strokes set as the standard for a particular hole.
A player scores an eagle when he or she hits the ball in the hole with two strokes fewer than par. For example, if par is five, a player scores an eagle by completing the hole in three strokes. Scoring an eagle is rare among recreational golfers. A typical eagle occurs on a player's second shot, after he or she has driven and is attempting to reach either the putting green or the area adjacent to the green.
A player scores a birdie when he or she completes a hole one stroke below par. Birdies are more common than eagles, more so among professionals and skilled amateurs. Golf historians believe that the term birdie first appeared in the United States around the end of the nineteenth century.
A player scores a bogey when he or she completes a hole one stroke over par. According to About.com, the term bogey was first used in the 1890s and, at that time, had a meaning similar to par.