What were we to do with these things? Some universities offered dialup access to their computer systems, but you needed to be a student to be able to do much. You might be working for a large corporation where your work is done on the remote system, while you're using a dumb terminal, or maybe your computer.
Somewhere around 1978 the first BBS was launched. I say around, because although there were some around already, the defining BBS style was put in place by two guys stuck at home during a blizzard. As the name suggests, it was initially a way to leave messages to other people, much as you'd leave paper notes on your fridge for family, or a noticeboard at work.
It didn't really take long from there to take off, with "doors" a seperate piece of software often games, that a launched by the BBS and look like part of the system. Message networks, a way to take messages from all the individual systems and share them across all manner of linked systems. It might have been a little slower, but you could get a message around the world. Of course there's also file transfer, the early 80's in particular was a hey day of computers of all sorts. Apple IIs, Z80 based CP/M systems, Tandy, Altair, Cromemco, Commodore PET and Vic20's before 64's arrived . They all needed their own kind of programmes, and BBS' would often keep quite large, well manicured files for the computers they had an interest in. It also made a great distribution point for all sorts of software written by Bob down the road, or even professional programmers with software that a publishing house didn't pick up. Here you could get software for free or a fairly modest fee.
So to sum it up a BBS is: