I felt the same way when I got to the tribute page project. I happen to also be going through video lessons on a different site (teamtreehouse.com), so I did their Bootstrap lesson to supplement. What I learned was, you can get a lot out of the Bootstrap documentation.
Here is the link to the documentation: https://v4-alpha.getbootstrap.com/getting-started/introduction/
On the right sidebar, under Layout, Content, Components, and Utilities, it will expand when you click those and you can see the different classes you can add to your HTML elements to make them appear different ways, and there are examples of how that will look.
I would try to explain how I understand the rows and columns, except my 3 year old is waking up from nap and I know I'll never finish if I don't just post this response now! Sorry!