As Mandela aged, he became more and more aware of the injustices of Apartheid. He became active in the African National Congress, and eventually joined Spear of the Nation, or MK, the terrorist/military arm of the ANC. His earlier passive resistance activities eventually gave way to the violence of MK because he felt non-violence wasn't getting the job done.
Mandela was imprisoned on an island by South Africa. He spent twenty years there before the ANC persuaded South African president F.W. de Klerk to release him.
Mandela became the first black president of South Africa.
The authorized biography of Nelson Mandela was written by [Anthony Sampson]?, ISBN 0-6797-8178-1 (amazon.com, search)