they're just cables with a load of wires in parallel so you can send parallel signals down lots of wires at the same time
I'm just using a couple of hacked up old IDE cables so I can send a 19-bit binary number to the RAM's address bus ("give me the contents of the memory cell at address 127637")
they're less common nowadays because parallel buses have fallen out of favour and serial buses are more fashionable, where you send the bits one after the other in packets synchronised to a clock (USB being the prime example)
I'm just using a couple of hacked up old IDE cables so I can send a 19-bit binary number to the RAM's address bus ("give me the contents of the memory cell at address 127637")
they're less common nowadays because parallel buses have fallen out of favour and serial buses are more fashionable, where you send the bits one after the other in packets synchronised to a clock (USB being the prime example)