Chapo Trap House is a leftish comedy podcast with three (later four, then five, now back to three) hosts that knew each other from twitter. It mostly commented on happenings in politics with regular segments going over the latest right wing bullshit, and was one of few places that would criticize the democrats as well. The /r/chapotraphouse subreddit was nominally for discussion of the podcast but it quickly outgrew that and became a general-purpose left-wing subreddit with a focus on irreverent shitposting and hostility towards outsiders. Fast-forward a bit and the podcast hosts remark that they don't like the subreddit anymore because people were criticizing them for various things, but nonetheless the subreddit continued to grow. A long-running joke that the "official podcast of the subreddit" was actually an entirely different podcast called Citations Needed began.

/r/cth was getting too big for the admins at reddit (one of whom thinks he'll own slaves in the post-apocalypse to give you an idea of their politics) and was banned for ill-defined reasons of "promoting hate" against slave owners (perhaps the reddit admin was insulted by this). In the aftermath of the banning, some people got together on a discord channel and a variety of volunteers got to work creating the website chapo.chat using lemmy. A couple months(?) later, chapo.chat was complete, though it forked from lemmy relatively early on and would be unable to federate for some time. A variety of comms were made, including /c/chapotraphouse, which then was ostensibly for discussion of both Chapo Trap House and Citations Needed, though this wasn't enforced or anything.

After some time, the admins decided to change the site name from chapo.chat to hexbear.net, because they no longer wished to associate with the podcast. In a completely failed attempt to encourage the growth of other communites on the site, the default "Main" comm was closed. Rather than this leading to the increased use of other comms that the admins were hoping for, /c/chapotraphouse became the new default comm. And finally, after much work from the dev team, hexbear.net reverted back to lemmy and was able to federate.

In summary: Chapo Trap House is a podcast.