Not taling about public transport here so much is the interface on computers whether they are Mac or PCs, to communicate with peripherals,  a.k.a. outside devices. I would give credit for this graphic but I can’t remember where it came from and I’m looking for a clearer one

Some of these interfaces are not available in all machines for example PCI/PCI-E requires plug-in slot on what is typically a desktop machine- if you are a Mac user you need to pick one of the species of Mac pro tower machines for that because you will not be able to do it on a Mac mini nor any laptop