-It's an alternative course that is recognised internationally (hence the name)
-It is a very independent course compared to the hsc, however because you're not compared to the others in your cohort/state, everyone helps each other out and it is a more relaxed environment
-The IB requires you to do 6 subjects from 6 different groups.
group 1 - english
group 2 - a second language
group 3 - history, economics, psychology, philosophy, geography, etc
group 4 - science (includes DT)
group 5 - Maths
group 6 - an arts (you can trade this for groups 2-5)
each subject has a band 1-7. Your total mark is these subjects added up (so 7 x 6 = 42)
Then there is also car (creation, action service) where you have to do a set number of community service, etc
There is also TOK (theory of knowledge) and an extended essay which is an essay on any subject you do. You can get 1 point for this so it adds up to 42 + 1 + 1 + 1 = 45 points (equivalent to 99.95)
You have to do a minimum of 3 high level subjects (advanced subjects that touch on university stuff at times) with a maximum of 4.
Overall, it's just a different option to the HSC.
My school offers the IB, (they are a small group compared to the hsc cohort and they're all amazing friends).