Game genre
A game genre refers to the type of game. There are several game genres to date.
Platformer
A platformer is a game genre in which the player's character goes across "platforms" to get to the end of the area. Typical platforming games involve the character moving left and right, and jumping to overcome platform heights and obstacles. Platformers are very popular, and in fact, make up the majority of the fangames on MFGG.
Role Playing Game
A role playing game (or RPG) is a game in which you gain some form of experience which increases some stat relevant to the player. It has been argued that an RPG requires a specific sort of combat system, however a great many RPGs designed more innovative combat systems. While there are a fair amount of RPG fangames, they are not popular to make because they require much more for-thought and time to produce than most other genres.
Puzzle
A puzzle game requires the player to manipulate one thing, which in turn allows you to complete a task. There are not very many puzzle fangames, and most of the existing ones are considered to be of poor quality (for instance, Mallow Maze 2: Switch it Up).