Airlines divide the seats on a plane into economy class seats, business class seats and first class seats (although there are some economy class only airlines like Kulula, 1time and Mango airline - this is especially common on low-cost carriers). Business class seats are more comfortable than economy class seats, usually offering more legroom, a wider seat and the seat having a greater ability to fold back. Service is better for business class passengers - there are fewer passengers per air steward and they get given posher meal settings and better meals. The business class seats are usually closer to the front of the aircraft than economy class seats, allowing business class passengers to disembark first.
When checking in there is often a shorter dedicated queue for business class passengers. Before getting on the plane, business class passengers usually have access to a business class lounge in the departures hall of the airport.
For flights within South Africa, business class seats are available on SAA (South African Airways), Interlink Airlines (Cape Town - Johannesburg and Johannesburg - Durban) and BA (British Airways) flights. The low cost carriers (Kulula, Mango & 1time) don't offer business class seats.
Airlines have their own ways of referring to Business Class seats:
Air France refers to "Affaires"
British Airways refers to "Club Class"
SAA refers to "Premium Class"