BBS Software creates a platform for a online cyberspace community, using either a dialup or telnet access. Some BBS software even provides the ability to create a ISP "Internet Service Provider" level of activity. Some platforms allow the addition of hosting of websites and email address applications for business applications.
The fundamentals behind a BBS are simply the same as the internet having file download/upload, message base system, chat, searches, email, polls, user profiles, echo message areas, netmail, world news and reports and online interactive games.
The fundamentals of a Bulletin Board System are basically the same as any major portal you visit just simply by a different name.