Course discovery vs edx-search


I’m a bit confused about the difference between course-discovery and edx-search modules.
I want to get some course additional tags persisted on Elasticsearch by other_settings feature and I want to do this from another backend. If I understood I need to install the course-discovery module because the course_discovery call, made by javascript from LMS, has its token and cannot be replicated from a backend. Instead, the APIs exposed by the course_discovery module contacting the same Elasticsearch as edx-search provide developers with a tool to get additional tags from a course. Is it a correct way to do this or not?