Shiloh is most definitely fiction. It has elements of creativity and imagination that aren't based on real events or people. It's a creation of the author's imagination.
The significance could be that Shiloh was a major battle in the Civil War. Their meeting there might symbolize the convergence of different fates or storylines against the backdrop of this important historical event. It could also be a place where key decisions are made or relationships are formed that will drive the rest of the plot in the novel.
Onision, whose real name is Gregory Jackson, had a very complex and controversial relationship with Shiloh. Their relationship was marked by a lot of drama and public disputes. Shiloh was involved with Onision at a time when he was already known for his rather erratic behavior online. However, as time went on, it became clear that the relationship was not healthy. There were accusations and counter - accusations between them, which led to a very public and messy fallout. Many of their interactions were documented on various social media platforms, making it a very public spectacle for their followers to witness.
I'm not sure specifically as I haven't read it. But generally, it could be about a character named Shiloh and his or her experiences, relationships, and growth in a particular setting.
It can be considered a true story to some extent. The author might have drawn from real-life experiences or real situations to create the plot and characters in 'Shiloh'.