The easiest way to think about analog multi-track is to think of a multi-lane highway. A multi-track tape recorder has multiple lanes that run along side of each other. And on each lane on the tape, different parts can be recorded. This is accomplished by a set of multi-track heads which each have separate electronics to deal with each pathway individually.
Once the recording has been made, you can transfer this analog recording to a computer via a multi-channel analog to digital converter unit which will plug into an available USB port on your computer and will also have multiple analog inputs where you can plug in your mixer or reel to reel deck directly.And then you can run your computer recording program to transfer, edit and mix the parts.
And yes, if you make a mistake, you can re-record the part over again without affecting the other parts of the tape.
You should also know that for doing the initial recording on the reel to reel deck, you will also need a multi-channel mixer which will allow you to plug in your microphones and instruments as well as give you the means to to route each of those parts to the tape recorder and set up a cue mix so that you can hear each part alone or combined with the other parts.
Many of the people here who record with analog reel to reel decks don't bother with a computer at all and record and mix their entire project in the analog realm, just like every recording studio on earth did up until about 20 years ago when digital recording started to come into being.
You should try to do more research on the topic as hundreds of books have been written on the subject and many on-line resources including videos are also available. Do a search on google or you-tube and be prepared to learn.
And please remember that while its possible for us to answer each of the hundreds of questions you may come up with, its really an unproductive use of our time to re-write out what has already been said in other threads here or elsewhere. So if you do start asking a lot more questions and no one is answering them, that is the reason.
Cheers!
