The Four Noble Truths

"I teach suffering, its origin, cessation and path. That's all I teach", declared the Buddha 2500 years ago.
The Four Noble Truths contain the essence of the Buddha's teachings. It was these four principles that the Buddha came to understand during his meditation under the bodhi tree.

1. The truth of suffering (Dukkha)
2. The truth of the origin of suffering (Samudāya)
3. The truth of the cessation of suffering (Nirodha)
4. The truth of the path to the cessation of suffering (Magga)

The Buddha is often compared to a physician. In the first two Noble Truths he diagnosed the problem (suffering) and identified its cause. The third Noble Truth is the realisation that there is a cure.
The fourth Noble Truth, in which the Buddha set out the Eightfold Path, is the prescription, the way to achieve a release from suffering.
http://www.bbc.co.uk/religion/religions/buddhism/beliefs/fournobletruths_1.shtml