Have you ever wondered how a Gameboy game looks on the inside? Check this out:
The battery (type CR2025) is not part of every game boy game. In Pokemon Silver and Gold (and other versions) the battery is needed to save the game. If the battery is low, all saved games are lost. Other Pokemon versions and also the majority of game boy games use a persistent memory instead.
The battery is also used to control time based events like the day-night-cycle in the Pokemon versions.
The Logic ICs (Integrated Circuits) is a kind of electronic circuit and used for calculations within the game.
As you can see, the ICs are heavily connected with the Memory (produced by Hyundai). The memory is furthermore connected with the MBC – the Memory Bank Controller. They are used for bank switching to provide more memory space.