Again the best thing to do is read all the information at this link . The defense is an oral exam, open to the public. You give a roughly 30 minute talk on your research, followed by questions. This is like a blending of your senior seminar and your QE. You’ll have a committee which will include your SC members, any collaborators and/or co-supervisors, an external member (from another university, who will have read the thesis, given in some questions, but likely won’t actually be there) and a Pro-Dean, who serves as chair. They will ask you some tough questions, but don’t panic, by this point you should know your work so well that you’ll know exactly why you did/did not do all your work. After the question period is finished, you, and everyone else, are asked to leave the room while they deliberate. They’ll call you (just you) back in to deliver the decision (most times you’ll get accepted with revisions) and also tell you if they think your work is good enough to qualify for the honours title. It’s an extra honour meaning you did exceptionally well.
Now, you really deserve a beer!