Kasparov's blunder

The blunder may not be as bad as it might seem because if the mistake Kasparov made during this match is hopeless, Kasparov may quickly offered his hand in resignation. So what exactly happened here? Kasparov's blunder may only result in a material loss, perhaps a pawn or the move shattered his position. Others believed that Anand took a pawn with his queen which threatened to take away Kasparov's 2 rooks or the queen. Is this true? If anyone had a more accurate allusion of the match, please feel free to share your knowledge with us.