The life of a historical Buddha can be summarized under the so-called Twelve Deeds. These teachings were given by Buddha himself in the Lalitavistara-Sutra, which has been translated to English under the title "The voice of the Buddha" (s. literature list). Here, we have a description of the deeds of a Buddha. They are based on the decision of an enlightened mind to enter an illusory human body (emanation state; skt.: nirmanakaya) once again, to first learn and later work for the benefit of all living beings throughout a whole lifetime.

The decision to be born in a human form at a certain time depends on three conditions: on the wishes he made on his way towards enlightenment, on the power of his realization and on the fact, that at the corresponding time there are no Buddhist teachings available. At the same time, beings of an existing culture have to have reached a general degree of maturity and openness, which make it possible for a Buddha to start turning the wheel of teachings. If, moreover, there exist appropriate parents and a suitable environment, a Buddha appears in a human body as emanation state, so others can see him in his outside form and can learn from him.

First, according to traditional explanations, the enlightened mind of a Buddha comes down from so-called "Tushita Heaven", the realm "Full of Joy", to connect his consciousness with sperm and egg of his future parents. Throughout this, his mother has strong and impressive dreams.
After nine months, the boy is born in Lumbini, at the frontier between today's Nepal and India. At the time of birth and shortly afterwards, there are extraordinary circumstances, which show the special nature of this human to others at an early stage.

In the time after that, the future Buddha grows up under especially sheltered and protected conditions. He learns the abilities of the respective culture, as for example reading, writing, maths, fine arts, science and sports, showing exceptional performance in all fields. Because of his human warmth, his worldly achievements are exemplary to others even at this early stage.
But not only his intellect and body are trained well, but also his feelings. He gives joy and enjoys noble female company to join male and female qualities.

After his worldly training has been completed, his spiritual development starts. Though there have already been four historical Buddhas in our aeon (Buddha Gautama Shakyamuni is the fourth one), again he renounces his usual life, driven by the deep, compassionate wish to overcome the suffering of beings.

At first, he does this by performing ascetic practices. He learns from teachers, who in times of spiritual openness and tolerance, are also searching for enlightenment, but have not yet found it. The future Buddha always reaches the level of his respective teacher very fast and then searches for another one.

His path leads him through great obstacles, which bring his body close to the door of death.  Finally, because of his experiences, he gains the deep insight, that the way to overcoming all suffering is beyond extremes. Based on this understanding, he finds himself a place, where he decides to stay, until he completely experiences enlightenment.

Buddha sits down below a fig tree, the famous Bodhi Tree in Bodh Gaya, North India, and meditates. He is motivated by the strong wish to overcome suffering for all lifetimes, and to let all beings, who wish to do so, take part in his experiences. Of course, the ego fights this. His last negative karmic impressions – traditionally called Mara – appear in his mind and try to flatter the ego, to trick it and to frighten it. But the future Buddha is no longer impressed by what appears in his mind. Thus, at dawn of full moon's day in May, at the age of 35, he overcomes the last subtle veils and reaches complete enlightenment, the state of omniscience.

Now, he can call himself Buddha, the "Awakened One", and starts "turning the wheel of  enlightened teachings". This means, that now he shows the way towards liberation from suffering to all people.  In his teachings, he addresses all beings. He gives to them what they need and understand, depending on their abilities and situation. Doing this, Buddha does neither distinguish by origin nor social state.
After altogether 45 years of teaching, Buddha dies in Kushinagara from food poisoning. He "enters Parinirvana" and thus shows the impermanent nature of conditioned existence.

This general resume of Buddha's life is not unique; in fact, these Buddha deeds are repeated as long as there exist any worlds at all, where Buddhas show themselves and the suffering has not ended for all beings.
Here comes a survey of the Twelve Deeds:
1. Coming down from the realm "Full of Joy"
2. Entering his mother's womb
3. Birth
4. Studying craftsmanship and arts
5. Enjoying life in the palace
6. Renunciation
7. Asceticism
8. Going to Bodh Gaya
9. Overcoming the powers of all obstacles
10. Enlightenment
11. Turning of the Wheel of Dharma
12. Entering Parinirvana