In Buddhist teachings, the term 'kilesa' (in Pali) or 'klesa/klesha' in Sanskrit, is translated as 'poison','defilement', 'affliction', or sometimes 'unwholesome root'. In any case, it refers to those states that most separate us from our own enlightenment, or awakening. Working to recognize these states as they arise in our consciousness, and to discover and release their roots in our psyche, is a foundation part of Buddhist practice.
As with most Buddhist concepts, exact teachings and translations differ between Buddhist branches. Some sutras mention 5 poisons, others 10, but the three poisons of anger, greed and ignorance are the most common, and considered the root poisons. They are the states that most clearly lead to suffering (dukkha) and obscure our recognition of our true nature. Each of them also has several 'companion', or associated, emotions and states:
Anger is associated with any rejecting or aversion-oriented emotion, such as hatred, animosity, being judgmental, hyper-critical, or easily irritated. These are all manifestations of 'otherizing' – separating ourselves from others and pushing something or someone away. The object of our aversion might even be an idea, as in the case of highly polemical political beliefs or other exclusionary belief systems.
Greed is related to any destructive desire or lust, covetousness, materialism, stinginess, possessiveness, jealousy, or a hoarding instinct. The operative words of this poison are 'must have','more' and 'mine'. When manifesting this state we are trapped in the idea that we must have something, or have more of it – whether a thing, a person, an addiction or an emotion – in order to be happy, and all else becomes lessened in our awareness.
Ignorance is at the root of all the poisons, and is built upon our basic misunderstanding of ourselves as separate and 'other' from our natural being, or enlightenment. Related states are delusion, passivity, being easily manipulated, and a lack of self-awareness.
We all have certain manifestations of these poisons that are our personal Achilles heel. Working deliberately to uproot them in our mind is an important part of the path. Doing so is not a matter of simply repressing them, or seeking to not express them by controlling our words or actions (although this can be a useful first step.) Instead, we need to honestly acknowledge them, and seek to clearly understand how they arise within ourselves. We need to recognize our triggers, and emotional patterns that contribute to them taking root. Meditation and mindfulness are important tools for helping gain the clarity and self-awareness required to do this practice.
Vajrayana or Tantric Buddhist lineages also focus on these poisons as energies that take root in our subtle or energy bodies through karma and conditioning, and include energy practices for releasing them from these levels. For example, the book Awakening the Sacred Body describes a breathe-based meditation purification practice designed to help us specifically surface and release the energies of the three poisons from the subtle levels of our being. Tantric chakra practices work in a similar way. The focus is not only on releasing blocks, but on transmuting the raw energy behind these emotions. For example, when the raw, aggressive energy that is normally behind anger is cleared of negativity, it supports positive, assertive, balanced action in the world. When the clinginess behind greed is cleared, the raw energy behind it supports an awareness of emptiness, or 'pure space', within which nothing is needed. And when the energy behind ignorance, or a sense of separateness, is dispersed, we are able to experience the bliss of 'oneness' and a true knowledge of our interconnectedness with all.
These are simple examples, but they point to an important point when working with the three poisons – that it is important to not to get caught up in punishing ourselves, or guilt, but instead to focus on acceptance and self-knowledge. Meeting ourselves where we truly are at, starting from a place of acceptance, is a cornerstone of all Buddhist practice. Otherwise, we may repress negative emotions instead of releasing and dispersing them, and then we cannot own the corresponding gifts that can accompany true insight.