IB has many diplomas. Most probably you are toalking about the higher year diploma. So in this diploma, you have to chose more a 'group of subjects' like sciences, business etc. It is pretty much the same as A level its just that this is not a british qualification, but Sweedish/Canadian/American one. It is far more practical, as in there is more field work and more science experiments. More info can be found on webpage that Q80 talked about.