We can think of game designers like chemists, except chemists that create mixtures of entertainment, emotionally driven narratives, and exciting experiences. If you think back to chemistry in high school, we all learned that some things make smoke, other things make bubbles, and a few things when combined make explosions; games work in a similar way, just with different substances (for example, game elements and mechanics).
When it comes to the distinction between these substances, namely game elements, and mechanics, there are many interpretations of what they are and what they are made up of. For the purpose of this book, when a player performs an action, they are likely to get something. This could range from a Badge, Point(s), Levels, or part of a Story. The "thing" that the player gets is what we will define as a "game element". Of course, there are many different examples of and perspectives on what game elements are, but for the purposes of this book, this will be our definition.
On the other hand, since game elements are the outcome, then the process of how we get them is what we will define as game mechanics. This could be anything from trading with other players, exploring mysterious worlds, and even Winning or Losing. Performing or engaging in these actions will result in obtaining game elements.