The N64 console needs the Jumper Pak to operate. The jumper pak is a small device that plugs into the front of the console under the small lid. It will not turn on or load a game without it installed, so as a minimum you need the black jumper pak that comes with the console or the optional red 4MB jumper pak for enhanced games. Yes, it's called the jumper pak and not "pack" which is just Nintendo's way of marketing the accessory.
The N64 was available with many accessories with the following list exploring most of them.
Nintendo 64 Power Supply- Supplied with the Nintendo 64 Console to provide power to the Control Deck And power the Nintendo 64.
Composite Cable - The Standard Cable that Came Packaged With The Nintendo 64 it Converts Standard Graphics Quality.
Stereo AV Cable- The Pal Version Of the Composite Cable But Includes a Euro Connector Plug which converts RCA composite and stereo cable inputs to Composite SCART.
S-Video Cable- S-Video Cable provides better quality than the regular composite cable and compatible with earlier SNES.
Jumper Pak- is a filler that plugs into the console's memory expansion port. It serves no functional purpose other than to terminate the RAM in the absence of the Expansion Pak it power the System On
Expansion Pak- consists of 4 MB of random access memory (RAM) increasing the Nintendo 64 console's RAM from 4 MB to 8 MB and of contiguous main memory is installed in a port on top of the console and replaces the pre-installed Jumper Pak you need an ejector tool like the dongle that was included with the Expansion Pak or just a Screwdriver for helping remove the original Jumper Pak.
Nintendo 64DD- is an official peripheral capable of reading and writing disks. It launched alongside a now-defunct online service called Randnet. With nine games released. The service was not only meant to play games over the web, but users could also chat, email, and access a virtual Nintendo newsletter.
Nintendo 64 RF Switch and RF Modulator - Made for the Nintendo 64 and for the second version of the Super Nintendo, it allows people with older televisions to be able to connect them to the two consoles. Later, they released a model for the GameCube.