I'm a noob, how does Rush work?

[xHeavenSentx]

Sorry, I'm completely new to BF.

So how does Rush actually work?

I get the attack and defend phase... and what to do during both phases... BUT... how do I know when I'm about to lose attack? 

I think I'm doing okay then suddenly it's game over and I lose.

This seems like a complete noob question I know

Edit: NM... got it.  I kept thinking the number on attack went up instead of down

[HempStCrew Don]

yeah, try and kill the attackers 75 time before they can destroy the 2 bomb sites...nice and simple. If you are attacking and you get a revive with the defib, that gives you another ticket[thats what they call the number of lives left] this is very helpfull when it seems all is lost and you only have 10 tickets left. I have seen matches go on for atleast 5 more minutes when there was less than 10 tickets left. I got a bomb planted by and defended with just two other teamates when we only had 4 tickest left. They kept killing my friends, but I would revive them... we just barely got the last crate but we did and ended up winning the enitre round.