The objective is to prevent the bomb from blowing up. even if you plant 20 bombs and none of them blow up your a useless terrorist.
and
The objective is to prevent the counter-terrorists from saving the hostages.
with the objective of killing the other team off topic.Originally Posted by http://en.wikipedia.org/wiki/CS_Source
And because it hasn't been said enough, what that phrase means is: the objective OF THE MAP. Not the team's objectives. When the rules mention the objective, it is what the map has you defending, or attacking.