Buddhism is a non-theistic religion.
We use this term, non-theistic, to differentiate it from both the atheo-materialistic and the theistic points of view. The theistic points of view are those advocating the existence of a personal Creator-God who is outside and above the 'creation'. Buddhism, especially in its Mahayana form, acknowledges the presence of such a 'living quality', which other religions call God, but did not consider it as an independent entity or being, pre-existing and separate from ourselves and 'things'. It calls it by many names such as Essence, Buddha Nature, Absolute Body (Dharmakaya), Spirit...
The recognition and full realization of this ever-present, indestructible Buddha Nature is called Enlightenment. Enlightenment is described as a state of perfect purity and development. The perfect purity is obtained when we completely dissipate all the veils that cover our true Buddha Nature: the veil of ignorance, the veil of dualistic tendencies, the veil of passions and the veil of karma. The perfect development is obtained when, having followed the path of enlightenment until its very end, we realize all the enlightened qualities inherent to our Buddha Nature: wisdom, love, compassion, power, and so on. Enlightenment is a state of wholeness, maturity and harmony that spontaneously accomplishes our own benefit and the benefit of others.
The non-recognition of the true nature of things produces a vicious circle of interdependent causes and effects, based on ignorance and its consequences, which is called Samsara. Samsara is an illusion experienced as alienation from our own true nature, incompleteness and suffering. Therefore, we can say that Buddhism is the art of transmuting 'a way of being' characterized by ignorance, confusion, selfishness and suffering into 'a way of being' characterized by knowledge, wisdom, compassion and wholeness.
To help us make this journey, the Buddha, the enlightened spirit, taught (and continues to teach) an infinite number of methods that correspond to the different inclinations, aspirations and capacities of beings.