I'm hoping there's a book or something out there for me to get...

If I have a class that has Collection as an instance variable, what is that method of coding called? A design pattern? If so, where can I find more information on it? As I've been working with this mentor, he's really helped me understand my programming weakness and that weakness is thinking in terms of collections or relationships between objects. It just seems so difficult for me right now and I need to read to become smarter. My mentor is a great guy, but he gets frustrated when I start asking lots of questions, so I'm starting to feel like I need to learn more on my own.

public class Evaluation
{
    private List<Criterion> criterion = null;

    public Evaluation()
    {
        criterion = new List<Criterion>();
    }
}