Goals are the result or achievement toward which players focus their efforts.
Good goals often follow the SMART pattern. That is:
Goals that are deemed difficult to achieve and specific tend to increase performance more than goals that are not.
Specific - A specific goal has a much greater chance of being accomplished than a general goal.
Measurable – When you measure your progress, you stay on track and experience the exhilaration of achievement that spurs you on to continued effort required to reach your goal.
Attainable – When a player can identify important goals, they want to complete them. They will see opportunities to bring themselves closer to the reward.
Realistic – To be realistic, a goal must represent an objective toward which the player is both willing and able to work.
Timely – In the world of games, this normally translates to giving the players an indication of progress. Certainly a timer or time-limited goal fits in this as well.
The lens is industry standard.