If you'd like a deeper dive into the philosophy of Discourse, the project -- what it is, what it set out to do, and why it exists -- I can recommend a few presentations and podcasts I've done over the years which go deeper on background than what you'll find on the Discourse home page.
2013 -- Forums Are Dead, Long Live Forums, presented at Forumcon
(You may want to follow the slide deck as you watch the video.)
2014 -- Learning versus Discussion, presented at San Francisco Community Managers
2015 -- User-Driven Product at Stack Overflow and Discourse, presented at Heavybit
2017 -- Civilized Discourse .. But How? presented at Heavybit
2019 -- Jeff Atwood on Discourse, Stack Overflow, and Building Online Community Platforms, with Jono Bacon
If you don't have time for a video, I recommend clicking through to the Heavybit presentations in 2015 and 2017 as they offer a complete transcript you can quickly read through if you prefer.
There have been other presentations and podcasts, but these are best ones for getting a broader sense of what Discourse set out to do.