Ebbie -

Both sides go into the game knowing that to win they will need to bowl the other team out completely, twice, and they have five days to do it. That's the game.
If the team batting last can't be bowled out by the end of the fifth day then neither side can be said to have won.

Although Jon is technically correct in saying that a draw is no result, it is tactically important over the course of a five-test series because now England & Oz each have one win and a draw, leaving only two more matches. At present Australia have the Ashes and will retain them with one more win. England need to win both the remaining games to take the Ashes. Australia can afford another draw, even a loss, England cannot afford either.

I expect that's cleared things up for you (grin).