How is subject connected to topics in course-discovery?

I am facing many understanding issues while working on course-discovery service because very less documentation is available for it. Please help me to get understanding on following points.

  1. I saw edx.org main page > Subject and topics cards how to get this relationship because when I saw discovery, I didn’t see any relation between both.
  2. How to fetch programs based on tags/topic and other filters. I saw in edx.org, programs are filter based on level, subject and other parameters but I couldn’t find way to do it in my case.

Let me know if somebody know about it and would like to clear understanding here.

Thanks in advance!!

It’s MARKETING SITE, you can build a MARKETING SITE using a CMS or whatever, and then put the link to your OpenEDX instance

I am supposing, marketing site also using course-discovery internally, That’s why need to understand relation of subject and topics

Exactly, you use discovery api to display courses and programs in your MARKETING SITE.

That is the trick.

I am using course-discovery api only but want show topics for subject and then filter programs based on it. I don’t know how to do it. Not able to fine good documentation as well.