Referencing is the way of showing that you have used the ideas of other people in your work. This includes things which you have read in books and journals or looked at online.
It would be unfortunate lose marks for lack of (or poor) referencing. On the other hand a clearly referenced piece of work will demonstrate that you have researched your topic well. Think of referencing as a positive tool; it is a way of making your work look professional and improving your grades. It truly need not be difficult.