Goals
In video games, a goal is a task or an aim that the player needs to achieve in order to boost the player's experience in the game. They are used to enhance the gaming experience in the game and to immerse the players in the gaming world. This is the main reason why developers need to create these goals so that the players have an aim and find the game more fun and less boring. Short term goals include killing an enemy, destroying a tower, activating an objective or simply scoring a goal. Examples of goals are unlocking a new gun in Call of Duty, completing achievements or acquiring an item for finishing a mission.
Challenges
Challenges are the longer version of goals. They are built from a game's goals and are either short term, medium term or long terms challenges.



Rewards
Rewards are ways in which the designer congratulates the player for being such a good gamer and playing their game to the point where they have unlocked rewards. Rewards boost the gaming experience and makes it more fun for the player. In video games there are two different types of rewards: short term rewards and long term rewards.
Short term rewards are really simple rewards. Things such as an extra life, an extra magazine or increased time to do the mission are short term rewards. In games such as CoD, the instant reward that players get when killing people is their equipment such as bullets, grenades and their guns. Long term rewards are more complex rewards and they usually take long to achieve. These are rewards such as experience, levels and skill points with which the player can improve their character and make it stronger by assigning the points they have achieved to a specific skill their character has. In games such as CoD and Tekken you could be rewarded with new gun skins and new characters to play with. These are mostly used so that the player gets stronger and feels like they are improving at the game.
Rewards are used within video games to keep the gamer from quitting. They are also used as prizes to give the players so that they are rewarded for playing the game. It would not be as good if you complete a game and not a single reward was given to your character. Also, players would ask themselves what was the point of all the time they spent playing the game if they do not get rewarded at all. So, it could be that rewards act as a reason for the gamer to play the game since once they receive rewards for completing the game the player can be proud of himself/herself.