Nelson Mandela was a south African anti-apartheid revolutionary and politician. Arrested in 1962, he was sentenced to life imprisonment after being convicted on charges of conspiracy to overthrow the state. He would spend there next twenty seven years behind bars. An international campaign to see him freed was successful when the last head of state F. W. De Klerk released him from Victor Verster prison in 1990. The two men would join forces to see the first multiracial and democratic elections in the country in 1994, resulting in Mandela leading the ANC to victory and his election as the first black South African president. He passed away in December 2013.
F. W. DeKlerk was the last head of state of south Africa in the apartheid era. Shortly after he became president he called for a non-racist south Africa to come into being . He also lifted bans on the ANC (African National Congress) and the Communist Party of South Africa and promised to release the anti-apartheid revolutionary Nelson Mandela. After his release, the men united to give rise to the first multi-racial elections in South Africa, in 1994. The two men are credited with helping to end apartheid.
Read about the negotiations here.