NASCAR. How does it work?

[gangajas]

I'm watching a NASCAR race (Talladega '06) for the first time and I don't understand how it works (It doesn't seem very complicated, but I suppose it has to have some complications). Do they go full throttle all the time? How fast they go? Are there any tactics involved?? They do anything special to overtake another car (I don´t know anything about ovals)? Why all the cars are almost identical?

Thank you