Hi Lioness,
Be careful about asking a webmaster to talk about the nuts and bolts, you could end up bored to tears! 
Each web server keeps "logs" of every server request, that record the IP (internet address) making the request, what pages were requested, and so on. Later, by analyzing these log files, we can determine 1) how many "user sessions" there were each day, and how many of them were "unique users." So, if you visited twice today, it would count as two "user sessions" but only one "unique user" (because the second visit was after you had already been counted once!)
Registered members are counted separately when people actively sign up for membership benefits.
Aus and Aries, there have always been far more "silent viewers" than active participants in the forums ... and that's okay, active participation isn't everyone's cup of tea. But of course the more interesting, loving, and helpful the forum discussions are, the more visitors take the plunge and become part of our visible community!
Greg