Sometimes people draw the line between people who write based on the length of their work. An author creates novel-length works, while a writer works in shorter segments.
Sometimes the line is drawn based on the content. Authors almost always deal in fiction, while non-fiction creators are writers.
Sometimes the differentiation is made based on publication status: a writer is a person who writes, an author has been published. I notice that the people who use this criteria tend to put self-published individuals with the non-published group, because their work hasn’t been approved by a traditional publishing house editorial staff.
I feel the main difference between a writer and an author is their attitude toward the work they do. A writer is someone, anyone, who writes. An author is someone who comes to their writing seriously, purposefully, and professionally. They take the time to learn how to write well. They learn the general rules of writing; they know how to construct a story arc, and they understand characterization, point of view, and the importance of research. They learn the rules of their genre, and follow them unless there’s a compelling reason to break them.
They also learn the rules of grammar. Spelling, punctuation, and proper sentence, paragraph, and chapter construction are vital for a well-written work. Grammar is the scaffolding that holds the story up. A beautiful story, badly told, is as difficult to wade through as beautifully told plotless drivel. I’ve even read badly written stories with no plot – but never for very long.
The good news is that this sort of professionalism can be learned. The rules are there, and there are many blogs and websites dedicated to good grammar, and to teaching the craft of writing. Good writers will take advantage of the free education that is available and produce good writing. They will become the authors of tomorrow.