How youtube works?

do they buy a domain, use apache, and use servers to stream flv?

i don't understand what program they use. is it apache or something?

would i need to buy servers if i was to expect 300 uploads/year on my site.

A quick google comes up with http://highscalability.com/youtube-architecture
Youtube is built with python, I did not know this. But that should have all the technicals you want.