Information on the Anglo Boer War can be found on https://angloboerwar.com/
The camps were formed by the British army to house the residents of the two Boer republics of the South African Republic and the Orange Free State. They were established towards the end of 1900, after Britain had invaded the Boer republics.
More information on the Bethulie Concentration Camp
More information on the Norvalspont Concentration Camp