Please give one example from popular culture that could be considered literature and one example that is certainly not literature.
The answer to this question depends entirely on how you choose to define "literature." One popular concept is that literature is a written work of considerable merit. In other words, the writing is great and the message is powerful enough to be timeless.
However, another definition of literature is less specific. This definition refers to literature simply as "written work that tells a story." The timelessness and quality of writing does not determine whether or not a book is "literature" by this definition.
I will give you answers to your question under both definitions of literature.
First definition (literature must have merit and be timeless):
A popular culture book that could be considered "literature" would be Life of Pi by Yann Martel. Published in 2001, this book is widely read and addresses the concepts of hope in the face of death, religion, and the bonds between man and animal. It is excellently written and will be read for many years to come. Another book you might consider is The Road by Cormac McCarthy. Written in a unique style with unquoted dialogue, this story of a father and son journeying through a post-apocalyptic world was an instant classic. The Road was published in 2006.
A popular culture book that would NOT be considered literature would be something like Twilight by Stephenie Meyer. While many teens enjoy these books for their themes of love and danger, the writing is not considered "great," and the books will probably not be read in, say, 100 years (when some new dangerous romance book will be popular). This book is not literature because it is not written "well," and because it will likely not stand the test of time.
Second definition (literature is written work):
You could use any of the above examples as literature in this case. Really, you could use any novel as an example. The only parameter here is that it has to be a written work. The worst novels, the best novels, and everything in-between could be considered literature.
It is harder, by this definition, to come up with something that is NOT literature. I would argue that something like a math textbook would not be literature. It does not have a theme or point, it is just numbers and explanations. It does not tell a story.
Hope this helps!
Like above, it depends on your understanding of the definition of literature. This could include newspapers or magazines that present pop culture topics, or maybe Humans of New York (literature through photography)
Random, non-academic social media (ie personal accounts)