Graphic novel

Graphic novel is unfamiliar format for me. It was first time get to k now about this term when I was taking writing studio class in here. Honestly I still don’t know what is the difference between graphic novel and comic. When I read the book called Understanding Rhetoric, I felt that it has too many words to say that it is comic. It looks like all the drawings exist for the texts. For me, when I looking at comic, I feel like drawings are main thing and texts are sub thing. Then what is the difference between these two that people generally think? Comic book has a single continuing series. It tells one story over many issues. Graphic novel has a single volume collecting the stories. It tells many storylines in one book.