Cartridge

A Cartridge is a plastic case, which has a PCB consisted in 2 ~ 5 ROM chips. Optionally, a cartridge can have a lithium battery (CR2032). Each ROM chip can hold Graphics, Program and/or Sounds.

NES cartridges

Any video game aficionado would recognize a NES cartridge, due to their case size. The NES cartridges have 72 pins (36 pins on each side), which two ROM chips: One holding the Graphics, known as CHR (CHaRacter) and other one holding the Game Code, known as PRG (PRoGram). Depending of the game, it can hold a proprietary chip, not to be precise from Nintendo. This proprietary chip is a Mapper. A Mapper expands the memory and the functions of the game, but only when the game is operation. There is a lot of custom Mapper, but the most popular series of Mappers are the Multi Management Controller (MMC). Example:

A Kirby's Adventure PCB have the following ICs:

NES-KR 0 CHR;
NES-KR 1 PRG;
Hyundai HY6264AP-10LL (CMOS Static RAM chip);
16-pin DIP Nintendo 6113B1 (lockout chip );
Nintendo MMC3C (third revision of the MMC3, a Mapper made by Nintendo);
CR2032 Lithium Battery (the battery manufacturer can be various, but mostly from a Japanese company, such as Maxell and Sony)

Famicom cartridges

Famicom cartridges, compared to the NES standards, is more smaller, in all aspects. Firstly, their change in a PCB is the pins, which have 60 pins (30 pins on each side), and you can add sound expansions, such as FME-7, a thing that US/PAL NESes cannot do. In order to play Famicom games on the NES, you need to buy an adapter, or open a very old NES cartridge, and dismount their adapter of their PCB. To play NES games on the Famicom and FamiClones, you need to buy another type of adapter.