Dependencies in Pure Functions?

So I'm taking a short L2 in understanding coding and what goes into it. I'm stuck on a question in my assessment that asks me to 'Identify potential dependencies or needs in pure functions'. Now I have a workbook that goes with this but it doesn't go into it much and simply asks me to research some examples to help me answer the question. The problem is I don't really know what I'm looking for as the workbook doesn't tell me what it is!

Anyone able to help or even link me a website that I can use?