Lemmy is the software a lot of the Reddit style fediverse websites run on. Many of them include Lemmy in the name such as Lemmy.ml and Lemmy.world, but others don't include Lemmy in the name. Beehaw.org is another website that runs the Lemmy software, it just didn't put Lemmy in its name. Beehaw does have an uncommon configuration since the down vote ability is disabled there, but it still is Lemmy at its core. Beehaw did defederate from some of the other big Lemmy servers because they were overwhelmed with trying to moderate that much content and those servers reportedly had open sign ups which led to a big influx of spammy bots, so Lemmy.world and beehaw.org are invisible to each other right now, but the admins of Beehaw have expressed a desire for more granular moderation tools in order not to have to defederate from such large servers as a whole in the future.
Kbin is a different software altogether so the kbin servers such as kbin.social and fedia.io have a different layout, terminology, and some different features than the Lemmy based servers, but Lemmy and Kbin both use the ActivityPub protocol to send and fetch data, so you can post between the two platforms as if they were on the same server. I am browsing this post and writing this reply from kbin.social.