vnc: What do I see after accessing the computer using tightVNC?

Regarding this question, how to verify if someone is connected to my laptop through TightVNC? I would like to clarify my doubts about tightvnc.

I have seen some videos on how tightvnc works and it seems that after a successful access, it will only show a screen with a few icons and a black background.

I wonder if you really see what I have open, p. Eg windows, files, etc. It says that tightvnc allows end users to control another computer's screen remotely. What does it really mean?

Thanks to all who can explain it to me.