They are looking for you to understand you USP (unique selling position), everyone has some unqiue qualities and experience, this requires you to have prepared well in advance and thought about you skills, knowledge etc. It is also a a variation of why do you want to work at Deloittes? So you need to understand what Deloittes values are and tailor your answer. They are a entreprenural culture so expect you to drum up work with out any partner direction. You need to be able to sell you self so this is the demonstration.