This is a utility package to serve as a base for linking org headings in various ways.
The idea is just to have a base package that provides a standard interface for building any type of functionality that works with a relationship between two headings.
It was originally extracted from an (aborted) rewrite of org-super-links. (it still exists and works on the org-linker-refactor branch if you are curious) and has since been used to build org-linker-edna. If you build something on top of it let me know and I will link it here as well.
You provide a callback function to org-linker and it will call that function with two markers. One in the heading where org-linker was called (SOURCE), and one in the heading of the selected target heading (TARGET). Then you can do whatever with those two markers.
The heavy lifting is done by org-ql via helm-org-ql.