What is “culture”? What is “pop culture”? Do you think that the terms “culture” and “popular culture” are easy to fix or define? Or, are both terms somewhat elusive?

I’m working on a communications multi-part question and need a reference to help me learn. What is “culture”? What is “pop culture”? Do you think that the terms “culture” and “popular culture” are easy to fix or define? Or, are both terms somewhat elusive? What does Chapter 1 point to as significant when considering the meaning of these terms?