The Nintendo 64 was a console made by Nintendo in 1996/1997. An add-on for the console known as the 64DD was released in 1999 - however, it was a commercial failure and its release was limited solely to the Japanese market.
In terms of overall emulation of the N64, the quality is subpar, but improved compared to earliest years of emulating the Nintendo 64. The main problem with N64 emulation is the use of plugins and that most emulators tend to use, by default, outdated and inaccurate ones. Some games are still problematic whether its sound issues such as Top Gear Rally or games such as Donkey Kong 64, Body Harvest, Pokemon Snap and Rogue Squadron. The ones that don't use plugins such as Cen64 and MAME are not at a stage of being useable due to the difficulties and the high requirements needed for accurate emulation.
There are two recommended plugins in the mean time: Angrylion RDP and GlideN64 (not to be confused with the old Glide64). The former is close to accurate graphically and even works on problematic games but requires a powerful computer to run the games and may not even run them at full speed on any computer in a couple of cases. The latter is not as accurate and still requires a fairly powerful computer but does run faster and some problematic games can be played using this. GlideN64 might not work if your computer has integrated Intel graphics, however.
Project 64 is the most known N64 emulator that also has some 64DD emulation as well. It can also be used to sprite/texture rip via a plug in.
mupen64Plus is the other well known N64 emulator and also runs on Linux too. While the emulator is commandline, there is a package available called m64p where it has the emulator, a GUI and the settings for GlideN64 all set up making it as close to plug and play as it can.
Dolphin is a Gamecube/Wii emulator that can emulate the N64 emulation used on the Virtual Console. If you do not want to mess with plugins and want to play on some of the more well known Nintendo games, it is an option.