Hi Chloe and welcome.
The British treated the Boers badly when they assumed control of the Cape in the early 1800s and brought with them English as official language (the Boers spoke Dutch, or at least, the beginnings of Afrikaans, the dialect that evolved away from Dutch into its own language) and the British legal system. Under Dutch rule, the Cape was essentially an anarchy, especially for those settlers who had ventured far to the east where they encountered the Xhosa. The British tried to bring them under governmental control, particularly when the British abolished slavery. As a transition, the "freed" slaves were indentured for 5 years, upon which the slave owners were to be paid a compensation for the loss of their free labour. The Boers were very upset about this, especially the fact that the compensation had to be claimed in London using the English language. What they essentially had to do was use an agent to claim their compensation, less fee, meaning they didn't get much compensation. They then assembled their ox wagons and trekked into the interior, forming their own countries, the Orange Free State and the Transvaal. The British left them be until they discovered gold in the Transvaal, at which point the British wanted it, no doubt inspired by the ruthless Cecil John Rhodes, who didn't care who he decimated on his way to conquests in the name of the Crown.
The British/Afrikaner relations came to a head on 1899 (actually because the Boers were treating the British badly in the Transvaal Republic, by not allowing those who had moved there with the discovery of gold to vote) when the Anglo-Boer (or as the British say, South African) War commenced. The British, as they say, won the war but lost the peace. The peace treaty culminated in the formation of the Union of South Africa in 1910, and the British copped out on the human rights issue by refusing to guarantee suffrage for all citizens in the new country. Instead they said that the new, white government could decide after independence, which guaranteed that the segregation and lack of universal suffrage would remain with the new government.
It was with the formation of the new country that the Boers started calling themselves Afrikaners (meaning Africans - they called Africans "Natives" or something much more offensive). Tension between English and Afrikaans speaking South Africans did ease a little after union, but escalated with the Second World War. Hendrik Verwoerd, and influential Social Scientist, Broederbond member and politician, had studied in Nazi Germany and liked what he saw. Many Afrikaners sympathised with the Germans, liked their Aryan ideas, and didn't see the need to enter into "England's War" despite being a member of the Commonwealth. When the prime minister, Jan Smuts, entered the war on the British side, opposition politics got a kick in the rear. In 1948, the National Party won the elections and with Hendrik Verwoerd's guidance, started to implement the policy of apartheid.
Now I somewhat doubt that this post will stand up as a reference for your history project, so see if you can locate a copy of A History of South Africa by Leonard Thompson. It is a very good, neutral telling of the history of South Africa, and concise enough for you to come to grips with in the time you have available, but detailed enough to satisfy your curiosity.
A History of South Africa - Google Book Search