He gained three knowledges: 1) past lives, 2) karma and its results, 3) liberation from afflictions/suffering/rebirth
See http://balawegaya.wordpress.com/2011/04/14/what-happened-under-the-bodhi-tree/
(Partial excerpt. Buddha said:)
“When my concentrated mind was thus purified, bright, unblemished, rid of imperfection, malleable, wieldy, steady, and attained to imperturbability, I directed it to knowledge of the recollection of past lives. I recollected my manifold past lives.
“This was the first true knowledge attained by me in the first watch of the night. Ignorance was banished and true knowledge arose, darkness was banished and light arose, as happens in one who abides diligent, ardent, and resolute. But such pleasant feeling that arose in me did not invade my mind and remain.
“When my concentrated mind was thus purified, bright, unblemished, rid of imperfection, malleable, wieldy, steady, and attained to imperturbability, I directed it to knowledge of the passing away and reappearance of beings. Thus with the divine eye, which is purified and surpasses the human, I saw beings passing away and reappearing, inferior and superior, fair and ugly, fortunate and unfortunate, and I understood how beings pass on according to their actions.
“This was the second true knowledge attained by me in the middle watch of the night. Ignorance was banished and true knowledge arose, darkness was banished and light arose, as happens in one who abides diligent, ardent, and resolute. But such pleasant feeling that arose in me did not invade my mind and remain.
“When my concentrated mind was thus purified, bright, unblemished, rid of imperfection, malleable, wieldy, steady, and attained to imperturbability, I directed it to knowledge of the destruction of the taints. I directly knew as it actually is: ‘This is suffering’; ‘This is the origin of suffering’; ‘This is the cessation of suffering’; ‘This is the way leading to the cessation of suffering’.
In the first discourses he said that he knew perfectly well these four truths as theory, their function and fulfillment of their function.
In the way he realized: ‘These are the taints’; ‘This is the origin of the taints’; ‘This is the cessation of the taints’; ‘This is the way leading to the cessation of the taints.’
“When I knew and saw thus, my mind was liberated from the taint of sensual desire, from the taint of being, and from the taint of ignorance. When it was liberated there came the knowledge: ‘It is liberated.’ I directly knew: ‘Birth is destroyed, the holy life has been lived, what had to be done has been done, there is no more coming to any state of being.’
“This was the third true knowledge attained by me in the last watch of the night. Ignorance was banished and true knowledge arose, darkness was banished and light arose, as happens in one who abides diligent, ardent, and resolute. But such pleasant feeling that arose in me did not invade my mind and remain.”[ix]
In particular it was the 3rd knowledge that is the enlightenment the Buddha attained. The first two are not supramundane attainments (even non-enlightened beings with samadhi can attain the first two to some degrees).
Taints:
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