The Dhamma that the Buddha realized is the Dhamma which exists permanently in the world. It can be compared to ground water which permanently exists in the ground. When a person wishes to dig a well, he must dig down deep enough to reach the ground water. The ground water is already there. He does not create the water, he just discovers it. Similarly, the Buddha did not invent the Dhamma, he did not decree the Dhamma. He merely revealed what was already there. Through contemplation, the Buddha saw the Dhamma. Therefore, it is said that the Buddha was enlightened, for enlightenment is knowing the Dhamma. The Dhamma is the truth of this world. Seeing this, Siddhattha Gotama is called ‘The Buddha’. The Dhamma is that which allows other people to become a Buddha, ‘One-who-knows’, one who knows Dhamma.
(Ajahn Chah)