“Bechuanaland” can refer to two different British colonial areas with (mostly) separate postal histories, both in the far southern part of the African continent:
British Bechuanaland (1885 — 1895)
British Bechuanaland used Cape of Good Hope overprint stamps. It became part of that colony in 1885, and the area is now a part of South Africa.
Bechuanaland Protectorate (1888 — 1966)
The Bechuanaland Protectorate was north of British Bechuanaland, and it used overprinted stamps from the Cape of Good Hope until 1932. That year, the Protectorate began using its own stamps. It gained independence and changed its name to Botswana in 1966.
Also see pages about either the north part (British Bechuanaland) or the south part (Bechuanaland Protectorate).