What is structure solution and design patterns?

I'm trying to response to the questions below and got no ideas what they are talking about. Can you give me and example and where to learn this? I have been working with .NET and SQL for a decade and never heard these question before.

1. How did you structure your solution and projects? I think I can say using Web API because it supports open source.
2. Do you apply any design patterns to your code and how did you separate your concerns?
3. What IoC did you use in your project and why? I think I know this one, the Unity Container.

These questions are related to the below paragraph.

We would like you to create a simple ASP.NET MVC web application for us. This will be the interface to interact with customer and order data we will provide you. Must be an ASP.NET MVC application. Must use SQL server as your database backend. A separate WebAPI project for your MVC application to use to interact with the data.