A minigame is a smaller, component game that is part of a larger video game. In a story-based game, this "game within the game" may be unrelated to the main story or goals. Minigames are often short, arcade-style games with a focus on casual, multiplayer gameplay.
In some games, the minigame is part of the story, required to progress further. For example, in the classic Sierra On-Line game, Space Quest III, the main character plays an arcade game called "Astro Chicken" (pictured). If the minigame is completed successfully, it gives the player a clue that's essential to winning the game.
In many popular video games, the available minigames are accessible from the main menu.