Put it simply for the wee man..
YES! Venomous snakes will kill you! Granted you can get treated with anti venom*, but as you are asking as to whether they can kill you or not, I would venture to guess that you knowledge is limited. The best bit of advice is this - you see a snake that looks annoyed/makes a rattling noise.. turn 180 degrees the other way and walk fast. If you can then see it from a safe distance, then enjoy the view.
*Which is damn expensive!
BTW guys, I hope you don't start corecting my English.. remember, some of us speak and write Queen's English
(And no, not the New York variety
)