Use this tag to refer to the "Fantastic Beasts" series. For questions about the 2016 film use the [fantastic-beasts-where-to-find-them] tag. Always use in conjunction with the [harry-potter] tag and add the appropriate film tag is asking about a specific film.
In 2001, J.K. Rowling wrote a small book called Fantastic Beasts and Where To Find Them. It was published for the Comic Relief charity, which according to the text in the book itself "was set up in 1985 by a group of British comedians to raise funds for projects promoting social justice and helping to tackle poverty". She also wrote Quidditch through the Ages for this purpose.
The Fantastic Beasts book looks like a facsimile of Harry's own copy of the book that appears in the Harry Potter series, including notes and comments by Harry and his friends.
In the Harry Potter universe, the book is written by one Newt Scamander. The 2016 movie Fantastic Beasts and Where to Find Them features his adventures in America. There are four sequels planned for that movie.
There are questions about the film over on Movies SE.