The number of people a balloon can carry depends on its size. At Cameron Balloons we build tiny one-man craft, some of which have a seat instead of a basket, up to monsters that have lifted 50 passengers. We generally say that a particular balloon will carry X people. More accurately we should say a balloon will carry so much weight at such and such a height and such and such an air temperature.
Big balloons tend to be used by commercial operators to carry fare paying passengers while more usual sizes will carry a large advertisement on the envelope plus the pilot and a couple of friends in the basket. More about these commercial considerations later.
Tastes change, but generally speaking the most popular size of balloon is described as a '77'. That's because the envelope holds 77,000 cubic feet (2190 cubic metres) of air. The 77 can often carry four people (depending on their weight!) which makes it ideal for family, club or syndicate use. In particularly warm climatic conditions, especially where the take off site is situated well above sea level, you might need an 84 or a 90 to carry four people. So the size of balloon you choose is dependent on how many people you want to fly, the air temperature and the location.