"I teach suffering, its origin, cessation and path. That's all I teach"
Four Noble Truths
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.
The truth of suffering (Dukkha)
The truth of the origin of suffering (Samudāya)
The truth of the cessation of suffering (Nirodha)
The truth of the path to the cessation of suffering (Magga)
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 way to achieve a release from suffering.
The First Noble Truth
Suffering comes in many forms. Three obvious kinds of suffering correspond to the first three sights the Buddha saw on his first journey outside his palace: old age, sickness and death. But according to the Buddha, the problem of suffering goes much deeper. Life is not ideal: it frequently fails to live up to our expectations.
Human beings are subject to desires and cravings, but even when we are able to satisfy these desires, the satisfaction is only temporary. Pleasure does not last; or if it does, it becomes monotonous.
Even when we are not suffering from outward causes like illness or bereavement, we are unfulfilled, unsatisfied. This is the truth of suffering. Some people who encounter this teaching may find it pessimistic. Buddhists find it neither optimistic nor pessimistic, but realistic. Fortunately the Buddha's teachings do not end with suffering; rather, they go on to tell us what we can do about it and how to end it.
The Second Noble Truth
Origin of suffering (Samudāya)
Our day-to-day troubles may seem to have easily identifiable causes: thirst, pain from an injury, sadness from the loss of a loved one. In the second of his Noble Truths, though, the Buddha claimed to have found the cause of all suffering - and it is much more deeply rooted than our immediate worries.
The Buddha taught that the root of all suffering is desire ( tanhā ). This comes in three forms, which he described as the Three Roots of Evil, or the Three Fires, or the Three Poisons, which are the three ultimate causes of suffering:
Greed and desire, ( represented in art by a rooster )
Ignorance or delusion, ( represented in art by a pig )
Hatred and destructive urges. ( represented in art by a snake )
The Third Noble Truth
Cessation of suffering (Nirodha)
The Buddha taught that the way to extinguish desire, which causes suffering, is to liberate oneself from attachment. This is the third Noble Truth - the possibility of liberation. The Buddha was a living example that this is possible in a human lifetime.
Nirvana means extinguishing. Attaining nirvana - reaching enlightenment - means extinguishing the three fires of greed, delusion and hatred.
Someone who reaches nirvana does not immediately disappear to a heavenly realm. Nirvana is better understood as a state of mind that humans can reach. It is a state of profound spiritual joy, without negative emotions and fears. Someone who has attained enlightenment is filled with compassion for all living things.
After death an enlightened person is liberated from the cycle of rebirth, but Buddhism gives no definite answers as to what happens next. The Buddha discouraged his followers from asking too many questions about nirvana. He wanted them to concentrate on the task at hand, which was freeing themselves from the cycle of suffering.
The Fourth Noble Truth
Path to the cessation of suffering (Magga)
The final Noble Truth is the Buddha's method for the end of suffering. This is a set of principles called the The Noble Eightfold Path, or sometimes the Middle Way. It avoids both indulgence and severe asceticism, neither of which the Buddha had found helpful in his search for enlightenment.
The Buddha described the path as a means to enlightenment, like a raft for crossing a river. Once one has reached the opposite shore, one no longer needs the raft and can leave it behind.
You can read these stages on the Noble Eightfold Path page