You're given rewards for accomplishing something exceptional or impressive, but usually do not convert to an in-game advantage.
Alternate names: Trophies, Badge, Award, Stamp, Medal, Challenge
The first video game about Achievements was released in 1997.
* Preferably only cases where the rewards have impact on gameplay. These however are almost non-existent.
* Preferably not achievements gained from normal play.¹ These however are the standard.
¹) for example: reaching certain population count in city building games, completing a level, beating a mandatory boss battle, etc.
Following rewards are less interesting:
* Unlocked difficulty levels
* Unlocked gameplay modes
* Unlocked story modes
* Unlocked levels
* Trophies with no gameplay impact
* Concept art, making of videos and other fancruft