this is a complex real time scalable system, to understand it ‘all’, all that it necessary is lot of hard work, learning tons of insanely complex details and generally going mad. Begin by reading the XMPP RFC for starters, when you are finished read the extensions, at this point you should post again someone may feed you the next ton of stuff to learn.
jitsi makes this process as easy as sending your friends the meeting URL . then , all your friends have to do is drop that link their browser of choice ( jitsi recommennds chrome, but in my experience firefox works just fine), enter the password,and they’re good to go.