Alternate history is a type of fiction set in a world where history has diverged from reality at some point. The plot usually revolves around explorations of the societal and political ramifications of those changes. It shares themes and elements with steampunk. In fact, steampunk's iconic The Difference Engine can also be classified as alternate history.
Well-known alternate history writers include Harry Turtledove and Eric Flint.
If you write alternate history fiction, explore the subgenre to connect with other like-minded writers, workshop, and publish your book.