The Kalahari covers an area of 1.2 million square kilometers and extends into 6 countries (Botswana, Namibia, South Africa, Zambia, Zimbabwe, Angola). The largest part of the Kalahari is in Botswana, the second largest in Namibia. Characteristics of the Kalahari are the red sand and Linear dunes. These dunes have since 10,000 - 20,000 years been overgrown with grasses, shrubs and trees and therefore no longer travel. The Kalahari is nowadays only a semi-desert. In large parts the average annual rainfall is about 500 mm. It is still called semi-desert, as there is little surface water. The precipitate immediately seeps into the sand and is absorbed by the vegetation. Nevertheless it habitats many animals. The most well-known animals of the Kalahari are the meercats, the Kalahari lion with its almost black mane and the oryx which is probably best adapted to the desert.

More information can be found here:
http://en.wikipedia.org/wiki/Kalahari