HSC and prelim Ag looks at a wide range of aspects of Australian Agriculture.
The core topics are Animals, Plants and product study, with options of: Animal managment, Plant managment, Horticulure, Agribusiness, Sustainable land managment and Innovation and diversification.
Most schools will focus on a particular animal/plant for the core subjects, and a specific farm product must be chosen (eg beef, milk etc). You can do two options or a research project in yr 12, but I don't think that many people opt to do the research project.
Like any science there is a practical component but I suppose this varies from school to school and depending on if you have an ag plot or not... Also, for younger years (9&10) there is a 50% prac requirement.
Its an interesting subject, the only thing I enjoy at school.