When one of the players goes all in a sidepot is created in order that other players can continue raising. If the one who went all in wins he doesn’t take this sidepot.
We have said it before, aggression is the key to making money and winning poker. Defensive play is not a good overall game plan: you won't win playing this way, but like playing loose, or weak bluffing, it is sometimes a useful tactic for hand by hand use.