Why did it occur?

As with most decolonization/independence conflicts of the era it can be traced to the rise of african nationalism, beginning in the 1870's but taking root in ernest in the first half of the 20th century.

The african nationalists opposed the white minority rule in Rhodesia while the white (and to some degree parts of the black population) saw the movement as a threat to their lifestyle. At the time there had been several bloody conflicts in other african nations such as the Congo Crisis and the Mau Mau revolt in Kenya. These were dirty wars partially fueled by African nationalism, white minority governments and cold war ideology.

Who was involved?

There were 3,5 main parties in the Rhodesian bush war;

• ZANLA/ZANU (Shona tribes)
• ZIRPA/ZAPU (Ndebele tribes)
• Republic of Rhodesia (White minority rule)
• Zimbabwe-Rhodesia (Non white minority)

In addition to this there were several international backers of the various factions. The Rhodesian government enjoyed the unofficial support of South Africa and Portugal. The ZANLA were supported by China, Libya and Tanzania. The ZIRPA enjoyed the support of the Soviet Union, Cuba, Zambia and East Germany.

And why in most photos that I have seen are the Rhodesian soldiers all white (Specifically Afrikaans looking)?

Because the most famous units of the war, namely the Rhodesian SAS, the Selous Scouts, the Rhodesian Light Infantry and several volunteer units were all-white. This was however an exception to the rule. The majority of the soldiers in the Rhodesian Security Forces were actually black.