A Journalist reacts, an author thinks.
A journalist works at covering news on a daily or weekly or even monthly basis, for a newspaper, magazine, television show, radio news, or Internet reporting. Most journalists are employees of the publisher, although some are free-lance. <br />
An author writes books, or poetry, or the occasional magazine article. An author is almost always self-employed, although he has remunerative contracts with publishers. Some authors work for publishing houses that print travel guides, or Idiots' Guides, etc.
Actually, in common usage, there might be little difference. There are "authors" who cover things that journalists cover. A difference might be that journalists write things "in the moment" while authors write for some degree of posterity. Yet, i always think of Mickey Spillane's retort. When asked about being an author, he replied, "Author? I'm a god damned writer. I get paid for my work."
Journalists are SUPPOSED TO report the news without bias or opinions. (Although, as we all know, that doesn't happen!) Authors have a much wider choice of medium, and are free to use bias/opinion.
A journalist is supposed to take the truth and report it to the people as a story. Authors tend to make up a story in order to demonstrate a truth.
A journalist gets paid, an author works for nothing.
A journalist reports, an author writes.
I think a journalist concentrates on facts and getting the non-fictitious story right. An author can right just about anything, but when you hear author, you may think stories and fiction.