How Reorder Posts stores order
A drag writes the WordPress menu_order column and, for hierarchical types, the parent. Deactivating the plugin leaves those numbers in place. Read more
Docs within "Explanation"
Why the admin order and the public order can differ
The reorder screen sorts by menu order. The public blog sorts by date until a query or the Advanced setting says otherwise. Read more
What this plugin orders, and what it leaves to other plugins
It orders published posts of the types you enable, including nested pages. Term order, front-end dragging, and drafts are out of scope. Read more