When you use another author’s ideas (and this includes paraphrasing, summarising and directly quoting someone), you need to say where you got it from.
In most cases, you are recording an author’s name, the date they published their work, the title of the work, and who published it.
Why is referencing important?
Not indicating when and where you have used someone else’s ideas is unethical. It’s also plagiarism. Your lecturer will assume that if something is not referenced, it is your own original idea. Both original thought and research are important skills to learn, and your lecturer needs to differentiate the two in your writing. It also allows your lecturer to fact check what you have written.