It is a concluding interview asked by your supervisor (and maybe teachers teaching in the field of your ee subject) before your final draft of your EE (basically IB wants you to have a feel of these interviews because you definitely have them in university for your dissertation and other research). The teacher will ask you about why you chose this subject, why to investigate on this topic (referring to your reaserach question) why this topic fascinates you to investigate it? The teacher might talk about the global issue of your topic (for instance if you investigate the women's role in two novels, the teacher might ask you abt how women were in the period of time in the novel). Others might include your methodology, how you investigate it, what tools you used to investigate it and why (maybe this is more asked on the social sciences and the sciences), what are your results and discuss your findings. Some basic/trivial questions might incl. what are your difficulties in investigating your EE, your limitations and weaknesses. Any times of frustrations (times you need to redo), how you learn from your mistakes, times when you feel very happy (might be after you hand in your final lol).
Although it looks like your abstract but i think you only need is to remember everything in your EE (know it quite well) and elaborate it and talk with your supervisor (and whoever is watching) your abstract --> it lasted 15 minutes for me.
Yeah again IB recommends schools to do it so that your supervisor can give (predict) your K mark (holistic judgement) in your EE, an area that the examiner whose marking your essay cannot judge.
As far as I understand (not doing mine just yet...) it's similar to how they approach your thesis in University. Your supervisor will ask questions about the work you did and why you did things the way you did. It's primarily just so the supervisor can check to see if you plagiarized. (So, for example, if your research seems very detailed but you don't understand any of it, it's very suspicious!)
But if you just know what you've written on your EE, then you should do fine. Think of it as an oral C&E Science Practical. Except not necessarily science.