About N64 Roms

[hell_fire_2021]

Now when I download an Nintendo 64 rom, it is in the format of *.v64. Now is that Nintendo's format or just a computer format. Like if I was to look at the files on the Nintendo cartage would I only see one file that has the ext. of .v64. If not what are all the files involved in a Nintendo 64 cartage and how can I change it back to its orginal format. Thanks for your help. Also I need some information on how the Nintendo cartage works.