Ra's al Ghul was the name for the head of the League of Shadows, who was responsible for leading them to destroy cities that had grown too large and corrupt.
Henri Ducard was the true Ra's al Ghul, but used a decoy when training recruits such as Bruce Wayne. The decoy accepted Wayne into training, and watched as Ducard showed him the techniques of the order. He was impressed when Wayne passed his test and discovered Ducard amongst a legion of soldiers. He then gave Wayne his final test - he had to execute a farmer who was convicted of murder. Wayne refused, and Ghul told him he was not ready to lead the men to their next target - Gotham City, which had grown very corrupt and needed to die. Wayne responded by setting fire to the building, and trying to escape. Ra's al Ghul engaged Wayne in a swordfight, but an explosion caused planks and rubble to fall and crush him to death.
The second decoy
Though Wayne escaped, Ducard planned Gotham's downfall using fear toxin. The League of Shadows invaded Wayne Manor, and another decoy Ra's al Ghul introduced himself at the party. When Wayne questioned him, Ducard appeared and revealed his true identity as al Ghul.