Alternate History is a Subgenre of Speculative fiction about what would happen if a event in history happened differently.
A quick history of Alternate History
Ab Urbe Condita Libri is possibly the first example of Alternate History written in Latin between 27 and 9 BC by the Roman historian Titus Livius it tells a story where Alexander the Great didn't die prematurely and Rome still beats Macedonia. This trope of the writers side still winning even though logically they should not is still a common trope in AH today.
Harry Norman Turtledove is a major author for AH and other works in the modern day and his stories have gone on to inspire many others.
How to get ideas for writing?
As Alternate History is about history the ideas are limitless. From making a small change in leadership or creating a massive change in how major events went down looking through history itself will give many ideas
Writing and story making
There are many ways to format your story. From telling it from the 3rd person or through the eyes of someone living in this world there are many options. Some use AH as a vector for making maps,flags ETC of alternate nations. Fake Wiki articles are also a popular format(please do not vandalize articles use the sandbox or other means)
conclusion
Alternate History is a fun topic to write about with endless stories just waiting to be written this guide will be updated as needed thank you for reading!