WordPress allows a hierarchy of parent Category divided into multiple sub-categories. Every post belonging to parent category can also belong to multiple sub-categories. By default, these posts are displayed in alphabetical order but you can group these posts by sub categories and then display them. This is called sub category wise list of Wordpress posts.
A classic example can be seen here . On this real estate site, all properties are sorted by their locations and every location is a sub category of the parent category called ‘Our Locations’.
There is no direct way to generate a sub category wise list of posts in WordPress. Here is a code snippit that can help you. This works for category pages.