Samsara ("all wandering together")is a concept in Buddhist teachings that can be defined as the "forced taking up of afflicted aggregates in a cyclical existence".
This means that a sentient being, who usually has the five aggregates (skandhas) dies, and then the afflictions in the mindstream of this being force them to be born again, in a way that is not controlled by them, but forced on them by their karma. It is this that creates the six realms of existence, and the types of beings in them.
These realms are:
All of these are marked by four things - they are impermanent, the cause and result of suffering producing afflictions, empty of any true existence.
But what are afflictions? They are the emotional and conceptual patterns caused by hate, clinging and confusion - these are the 'three poisons'. Through a basic confusion about the nature of the world and the self, various complexes and habitual tendencies arise in the mind, all based on the three poisons.
"Birth is stressful, aging is stressful, death is stressful; sorrow, lamentation, pain, distress, & despair are stressful; association with what is not loved is stressful, separation from what is loved is stressful, not getting what is wanted is stressful. In short, the five clinging-aggregates are stressful.
- Nibbedhika Sutta
A sentient being will find themselves reborn with aggregates that are the product of previous ones belonging to the same mind-stream, conditioned by them to appear a certain way. Without intervention, they will produce afflicted aggregates in the future.
What is the outcome of this? The answer, is suffering - dukkha. Beings experience things they dislike, or things they crave. Such an experience means they are constantly struggling, and unfortunately, due to their confusion, fail to see that it is this struggling that is the main cause of propagating samsaric existence.
Suffering is split into three main forms:
- The suffering of suffering
- The suffering of change
- The suffering of conditionality
The first is that beings experience pain and discomfort. Things can be unpleasant at times, and we can spend our time running after external things to make us happy.
The second is that all things are impermanent, and any happiness gained is not going to last. Things we like may become things we dislike, or pleasant things may be taken from us by impermanence. Importantly, we get ill, we get old and then we die.
The third is that we are bound by karma, and our minds and bodies are forced in certain directions due to habitual tendancies. Although we have some control, we are forced to reap the results of past actions. This is the most subtle level of suffering, only clearly perceptable to those who have gained a certain degree of insight and are approaching liberation.
To one who experiences sensations, meditators, I teach the truth of suffering, I teach the truth of the arising of suffering, I teach the truth of the cessation of suffering and I teach the truth of the path leading to the cessation of suffering.
- Anguttara Nikaya
The whole point of Buddha's teachings is that this state can be escaped. Samsara has causes. These are the three poisons. Destroying the poisons will destroy the cause of suffering, and bring it to an end. The way to do this is to follow the eight-fold path. These are the four noble truths. The result of following the eightfold path is liberation from samsara, which is the attainment of nirvana. This is a state of existence where the mind is completely at peace and undisturbed by afflictions, and suffering is permanently trancended. It is not mere non-existence, as some mistakenly put it, but a which state beyond all possible conceptualisations about it.
It's good to hear some more words of the Buddha on the subject.
"Long have you (repeatedly) experienced the death of a mother. The tears you have shed over the death of a mother while transmigrating & wandering this long, long time -- crying & weeping from being joined with what is displeasing, being separated from what is pleasing -- are greater than the water in the four great oceans.
"Long have you (repeatedly) experienced the death of a father... the death of a brother... the death of a sister... the death of a son... the death of a daughter... loss with regard to relatives... loss with regard to wealth... loss with regard to disease. The tears you have shed over loss with regard to disease while transmigrating & wandering this long, long time -- crying & weeping from being joined with what is displeasing, being separated from what is pleasing -- are greater than the water in the four great oceans.
"Why is that? From an inconstruable beginning comes transmigration. A beginning point is not evident, though beings hindered by ignorance and fettered by craving are transmigrating & wandering on. Long have you thus experienced stress, experienced pain, experienced loss, swelling the cemeteries -- enough to become disenchanted with all fabricated things, enough to become dispassionate, enough to be released."
- Assu Sutta